Hey @Ronnie Jorgensen I don't see why it wouldn't work.
The Pin and Biometrics are client side, for unlocking the device to get access to the AuthToken HMAC key, per the Android docs : https://source.android.com/security/authentication
I assume that iOS follows a similar flow, and this should allow access to the app. If pin and touch ID works, then biometrics should also work, as those authentication methods are device centric.
The actual workday app is most likely constantly refreshing the token as it follows the flow described in the Microsoft AAD SSO docs here : https://learn.microsoft.com/en-us/azure/active-directory/manage-apps/what-is-single-sign-on#choosing-a-single-sign-on-method
More info here on implementation specifics : https://learn.microsoft.com/en-us/azure/app-service-mobile/app-service-mobile-auth#authentication-with-provider-sdk
If you're interested in learning more, I would suggest asking Workday as they are the ones who actually implemented the application and would know more on what is supported vs not supported.