@Joseph P. Gallagher, Thanks for posting in Q&A.
Based on my testing, I can enroll two devices into Intune using the same account and when I login in one PC using the AAD account, it will not take out another PC.
To clarify this issue, please check the following.
1.Check if the account has Intune license and a Microsoft Entra ID P1 or P2.
2.Check if enrolled devices more than 15 in the account.
3.Check if exist Multiple User enrollment on the targeted devices.
If there is any unclear, feel free to let me know.
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