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.
I’ve recently purchased some USA Pan loaf pans from the Community Loaves supply site. The Use and Care instructions with the pans indicates “Use of cooking spray is not recommended.”, which is contrary to the step by step instructions for baking the modern loaf. Does anyone know if there is a valid reason for not using cooking spray with these pans?