Your interpretation is creating an ambiguity when none exists. Your specific question is about 32 CFR 47.4 not applying to the National Guard; however, you hone in on a single phrase while ignoring literally everything else about the regulation. So, there are additional things you look at:
The purpose of the part. This part has a nice "Purpose" section at 47.1, which says it implements PL 95-202 and
Directs the Secretary of the Air Force to determine if an established group of civilian employees or contract workers provided service to the U.S. Armed Forces in a manner considered active military service for Department of Veterans Affairs (VA) benefits.
Also, its title is "Active duty service for civilian or contractual groups." Members of the National Guard are not civilians. It would be surprising (to say the least) if they fell under this part, given that the clear purpose is to say "some civilian service to the military is not just a normal civilian job; these people deserve benefits given to people who are formally in the military."
Surrounding rules. For instance, the definitions in 47.3 require that a group, to be a "civilian or contractual group" within the meaning of the part, be similarly situated to the Women's Air Forces Service Pilots.
Statutory authority. All parts of the CFR need to be made under authority granted by Congress; the authority for 32 CFR 47 is a federal law codified as a note to 38 USC § 106 (and passed as PL 95-202 § 401(a)) saying
the service of any person as a member of the Women’s Air Forces Service Pilots (a group of Federal civilian employees attached to the United States Army Air Force during World War II), or the service of any person in any other similarly situated group the members of which rendered service to the Armed Forces of the United States in a capacity considered civilian employment or contractual service at the time such service was rendered, shall be considered active duty for the purposes of all laws administered by the Secretary of Veterans Affairs [if they meet DoD regulations to qualify for it]
Administrative agencies are given a great deal of deference when interpreting the statutes they base their regulation on; however, they can't really not require that a group be similarly situated to WASPs, because the statute they're saying groups can qualify under requires that groups be similarly situated to qualify.
To answer your question about whether the National Guard gets benefits: Members of the National Guard are simultaneously members of the Army or Air Force reserves. This regulation lets certain civilian groups count as active duty, leaving it up to DoD who qualifies. For the military, there's no need to leave it up to DoD who qualifies; Congress is quite capable of simply defining what the military is. Under 38 USC § 101(21), "active duty" means, among other things, "full-time duty in the Armed Forces, other than active duty for training."
When the National Guard is on full-time military duty other than for training, they are on active duty, because that is what that phrase means. When they aren't, they aren't. At no point do they qualify because they are civilians in a similar situation to WASPs (which is the sole purpose of this part, to let those people qualify) due to their National Guard service; they are qualified because they are actually in the military, and not because some special policy means they qualify when they otherwise wouldn't.