What is the point of this hardening feature if you got to disable it ?
You can tweak Android as much as you want, the OS was not made to be private nor secure. App developers will never check if it breaks the grapheneos memory allocating feature (amongst others) so by default you disable it.
Anyway it also requires the app to be able to even run on a rom that doesn’t respect play integrity.
It's meant to protect apps against their own bugs. It's an improvement to be enabled by default and disabled for the few apps where it's an issue.