Huh—my experience with having my credit "frozen" was that I could still open accounts, it just meant that if it was happening online the company would call me first using some number on record with the CRAs (I think?) to make sure it was really me (and, like... why the actual fuck isn't that the default behavior? Why do you have to request that they do that?) I'd not have even bothered unfreezing before trying to app…
I feel like freezing should get you a set of 10 one-time defrost codes. When you apply for something, you give a defrost code to the creditor and that lets them punch through. When you run out, you can re-authenticate and get more.
The normal unfreeze process could still work, but frozen really should be the default, rather than this weird freeze / unfreeze business you have to do. What we really want is to grant one creditor access one time.