@Brian C , After researching, I find there are app configuration settings "IntuneMAMAllowedAccountsOnly" and "IntuneMAMUPN" we can configured to limit access to only allowed organization user accounts and block personal accounts within the apps. Here is a link with more details for the reference:
https://learn.microsoft.com/en-us/mem/intune/apps/app-configuration-policies-use-ios#allow-only-configured-organization-accounts-in-apps
Hope it can help.
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