Yes - that's the situation.
I wrote to the "IO app" support and they told me that --> (deepl translation):
When you activate Documents on IO, the system generates a "Wallet Instance" (a cryptographic wallet instance) that is permanently linked to that specific physical device.
The technical infrastructure does not perform any “proprietary” checks to validate the security of this “Wallet Instance”, but relies strictly on the integrity APIs provided by the operating system manufacturers: Play Integrity API and Key Attestation for Google/Android, and DeviceCheck for Apple.
If these APIs detect that the device has been tampered with (e.g. rooted, although this is not the case for you) or that it is running a non-native operating system or Google services (as is the case with GrapheneOS and others), the infrastructure blocks the creation of the Wallet Instance, returning the ‘integrity check failed’ error that you encountered.
I kindly asked to forward this internally to have it fixed - I don't count on it, but anyway...
I'll go over to GitHub as well.