Hi @JustinMicheal-7973
According to my research, it seems that o365 ignores the accountExpires attribute, so the account will still be able to access the resource. And I see other users encounter this issue as well.
However we could use the solution below to solve this issue:
How to make Azure AD Connect disable expired accounts
And this thread discussed this similar issue for your reference: Office 365 ignores expired accounts and continues to allow access
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