I do not agree with a sealed record is not sealed from law enforcement.
Put simply, if a record is sealed it is sealed. Specifically, when a record is sealed a right to privacy attaches. See, Gonzalez v. Spencer, 336 F.3d 832 (9th Cir.), cert. denied 157 L.Ed.2d 253, 124 S.Ct. 334 (2003) (attorney and law firm liable for accessing sealed case file without court authorization) Thus, if a sealed name change is issued, law enforcement will not have records of it since the record is sealed. Only the Clerk of the Court has access to sealed records. See, Rule of Court, Rule 2.551 (f) Custody of sealed records:
Sealed records must be securely filed and kept separate from the public file in the case. If the sealed records are in electronic form, appropriate access controls must be established to ensure that only authorized persons may access the sealed records.
There is not a secret portal where police can rummage through sealed records, thus violating the expectation of privacy.
One common instance where a sealed name is disclosed is where the person changes his/her driver's license from the old name to the new name. That creates a data trail demonstrating who the person was and now is. DMV reports are sold to data brokers, accessible by insurance agents, claim adjusters, police, private investigators, and often anyone with a credit card. There are ways around obtaining a driver's license I will not discuss here, but they do exist and are legal.
Another way Government knows about your sealed name is by disclosing it to the SSA. However, local police do not have access to SSA records. The Privacy Act of 1974 (5 U.S.C. § 552a(b)(7)) permits, but does not require, a Federal agency to disclose personal information from its systems of records to another agency or to an instrumentality of any governmental jurisdiction within or under the control of the United States for a civil or criminal law enforcement activity if the activity is authorized by law, and if the head of the agency or instrumentality has made a written request to the agency which maintains the record specifying the particular portion desired and the law enforcement activity for which the record is sought. See SSA Policy here.
Yet, another way is when/if you fill out a form for virtually any government job, you must disclose any names you have gone by and attest to such under penalty of perjury. Depending on the job, you will undergo a polygraph too. Along with the application process is a waiver to access any all records.
Now, on the flip side, unless you demonstrate a risk of harm, your name change is likely a public record and prior to being allowed to change your name, you must announce to the world in a major newspaper for weeks. Only after showing proof of publication will allow you to change your name. Of course, there is no expectation of privacy in this instance.