Interesting workaround. I imagine this could in turn lead to more pressure on these same apps to implement Sign In with Apple - as a user, its email privacy feature becomes more interesting in this scenario.
https://developer.apple.com/app-store/review/guidelines/#sig...
I wouldn’t treat it as a privacy feature, I would treat it as a convenience feature. When I needed some extra mask straps, I installed Etsy, didn’t previously have an account. So I used Sign In with Apple to register, picked out some mask straps, and Apple Pay to pay. The whole process only took as long as it took for me to make a selection and two biometric authentications, but some of my information had to be exchanged in order to make that transaction possible.
Also I can login to UPS and Etsy without a password.