PayPal accidentally broke support for GrapheneOS with the default settings for the app by adding incorrect anti-tampering code. It can be worked around using the per-app toggle to disable secure spawning. It shouldn't be necessary and we didn't expect there to be apps incompatible with secure spawning so we didn't originally design it to have a per-app toggle and had to add it.
Several of the more aggressive exploit protections are enabled for the base OS but are opt-in for user-installed apps. Memory tagging should work with all user installed apps but is opt-in because it's so good at detecting invalid memory accesses and uncovers a lot of bugs. Dynamic code loading via storage, dynamic code loading via memory and native debugging are allowed by default since a significant fraction of apps need those and it's not usually a bug. Users can set those as enabled by default for user installed apps which is particularly recommended for memory tagging but then people need to deal with the incompatibilities. The defaults don't cause issues with most apps so not everyone is aware of the per-app toggles.