Does this setup mean, it is upon the defendant to spend filing fees
and put everything on record by filing that someone sent them a suit
so a judge can go and dismiss the plaintiff's case, which they didn't
After service on a defendant, (1) the defendant invokes the jurisdiction of the court by filing an answer or motion to dismiss, (2) the plaintiff invokes the jurisdiction of the court by filing a motion for default judgment, or (3) the parties by express agreement or implication waive the Minn. R. Civ. Pro. 12(a) deadline for a responsive to a complaint. The third case would usually arise either (1) because payment in full or settlement has made the case moot, or (2) because they are negotiating a resolution.
The Summons, Return of Service, and Complaint don't have to be filed with the court until one year after service of process on a defendant (unless mutually agreed otherwise) or the claims there were brought or could have been brought in the complaint are dismissed with prejudice. Minn. R. Civ. Pro. 5.04(a).
But any responsive pleading such as an answer or motion to dismiss must be served by the defendant within 21 days of service, Minn. R. Civ. Proc. 12(a), and any responsive pleading must be filed with the court. Minn. R. Civ. Pro. 5.4(b).
I'm not certain what filing fees apply in cases where an answer or motion to dismiss is filed before the summons and complaint: There is a $75 fee for filing a motion or response to a motion (which is unusual), and a $285 fee for a party's first filing in an ordinary civil action (which is common).
Failing to appear in response to a Motion to Dismiss would incur no new filing fees but result in a default judgment against the Plaintiff on the Motion to Dismiss together with a judgment for costs.
From the defendant's perspective the fees incurred in this scenario are the same as they would be if the Plaintiff had filed the case in the first place, and the plaintiff will pay the same fees that it would have otherwise if the Plaintiff responds to the Motion to Dismiss.
The Defendant filing the Motion to Dismiss is no worse off if the Plaintiff avoids the filing fee in the case by not filing a response to the Motion to Dismiss with the Court, giving the Defendant a default judgment on it (indeed, the Defendant is better off because no fees have to be incurred to write a reply brief regarding their Motion to Dismiss). Presumably, a prevailing motion to dismiss party is entitled, at a minimum, to a judgment for costs against the plaintiff in such a case. The Defendant might even receive an award of attorneys' fees a sanction as well, if the Plaintiff defaults in response to the Defendant's Motion to Dismiss, if the right conditions are met.
Of course, a Plaintiff can't get a court to enter a default judgment without filing the Summons, Return of Service, Complaint, a Motion for Default Judgment, and a Soldier's and Sailor's Relief Act Affidavit with the court.
Incidentally, service of a summons by certified mail on an individual is generally only allowed if there is consent prior to suit (e.g. in a contract). See Minn. R. Civ. Proc. 4(a).
Analysis and Context
A few observations about the Minnesota Rule:
Minnesota does not permit a party who can't manage to get a defendant served with process because the defendant can't be located by a process server to preserve their statute of limitations by filing a complaint with the court and then serving the summons and complaint within a reasonable time afterwards, unlike federal court and most state court systems. This has the potential to be quite harsh in effect.
Statutes of limitations are automatically tolled pending negotiations up to a year, when there is service of a summons and complaint followed by negotiations rather than a filing of the case with the court.
Hip pocket service allows a debt collector to make sort of a "super demand notice" in which non-compliance results in not just a threat to sue in the future but immediate filing of a lawsuit which damages the defendant's credit rating in a public record. This extra nudge on a defendant who is well off enough to care about a credit record can make collection more likely to be successful especially in cases where the defendant has not viable defense to assert in good faith in an answer.
Hip pocket service probably slightly reduces the case load of routine default judgment or immediate voluntary dismissal cases.
Hip pocket service was probably instituted originally to end the need to have courts issue an alias summons when a defendant couldn't be timely filed back in the days when a summons had a date certain return date and had to be served a certain number of days prior to the return date, rather than requiring a response within certain number of days after service of process is achieved as modern Minn. R. Civ. Pro. 12(a) provides (which was an innovation first widely adopted by states in the 1930s in following the adoption then of the federal rules of civil procedure which used this procedure).
The linked article in the question does a good job of explaining the process.
The older date certain return date hasn't vanished, however.
Colorado, for example, has a hybrid version of this system using the federal response within days of service model for its general jurisdiction district courts, and also allows for hip pocket service but with the requirement that the complaint be filed within 14 days of service. Colo. R. Civ. Pro. 3. It also allows for fixed return date with hip pocket service for its limited jurisdiction county court civil actions.
New York State also has many circumstances with date certain return dates in the form of Order to Show Cause practice that is common there.
But, at the linked article notes, post-service out of court process in Minnesota and two other states is much more extensive than in other states.