I’ve wondered about this too. Tomorrow I will leave one of the 8 loaves in USA pans without pan spray to see what happens and report back.
What I have found in these months of baking is that all pan spray is not created equally. Mostly I have used Spectrum Organic Sunflower Spray, which I buy at PCC. But a while back they had none of that and instead I had to get a different one. I think it was Field Day Olive Oil spray. Very different consistency. The Spectrum seemed like an aerosol, the Field Day seemed like just spraying oil. The Field Day spray was a disaster. I used piece of parchment and the FD spray (in a non-USA pan). I could not get the loaves out. The corners stuck terribly. I had 3 loaves that were not donate-able because they looked like mice had eaten them!
When I read the instructions on the USA I was thinking they did not want you to use something like PAM spray. That stuff seems sticky and sort of bonds to what you spray it on eventually. I also wonder what the USA pans will do as they age. I have USA sheet pans that are no longer as non-sticky as they used to be. They’ve gotten a lot of hard use.