Same issue here. I've used Xcode 13.2 beta 2 with macOS 12.0.1 without this issue.

Currently the API is limited to macOS, but I don’t know the reason they decided to exclude iOS. The latest iPad uses M1 chip, so apparently there is not reason to exclude iOS to create 3D objects. I’ll appreciate if Apple engineers can explain us why is limited to Mac or it will come to iOS in future betas.

Thanks for your reply! I'm using a 2018 Mac mini, so definitely it's not supported.