>that implies that a "certified Android" device capable of Play Integrity attestation is required

No, it doesn't. It implies that the app for handling the deeplink lives within GMS as opposed to needing to manually install a separate app like you do on iOS. GMS does not have a hard dependency on device integrity APIs being supported.

They said "capable of Play Integrity attestation". It's a weasel statement. If you have GMS, you're capable of performing PIA attestation, you just might fail. So it's strictly true, but doesn't tell us anything about whether it requires PIA.