With the passage of the Economic Growth, Regulatory Relief, and Consumer Protection Act which was signed into law on May 24, 2018, security freezes do not apply to the making of a credit report for use in connection with "employment, tenant, or background screening purposes" (see Sec. 301(a)(4)(I) of the Act [page 34 of the PDF below]).
https://www.congress.gov/115/plaws/publ174/PLAW-115publ174.p...
To be fair, I'm not sure if the same rules apply to whatever type of "freeze" the work number offers. I'm not even entirely sure it's regulated at all.
I agree that it is actually pretty confusing what kind of "freeze" The Work Number offers when you do it, especially since The Work Number does not distinguish between hard inquiries and soft inquiries and groups both together as "Verifiers who have procured or attempted to procure your data in the past 24 months". Most freezes only block hard inquiries, which involve the extension of new credit. Background checks typically come in as soft inquiries and therefore bypass security freezes. Oddly enough, there are some companies that extend credit even with soft inquiries, so a security freeze will not stop fraud there.
That said, I have seen anecdotes online that say that when somebody pulls a frozen The Work Number report, it comes back as blank even if there is information in the file. This is different than how freezes are handled elsewhere. Most places just report back that the report is frozen when a frozen report is requested. They do not imply anything about the state of the information in it.