From the documentation on Google Play Integrity API, the purpose of this API is to …
… check that interactions and server requests are coming from your genuine app binary running on a genuine Android device. By detecting potentially risky and fraudulent interactions, such as from tampered app versions and untrustworthy environments, your app’s backend server can respond with appropriate actions to prevent attacks and reduce abuse.
For SAB apps, there is no backend that we need to protect (e.g. user account licensing, monetary transactions, etc).
I do not believe this is relevant. Thank you for bringing this to our attention.