@amartinez_admin Thanks for posting in our Q&A.
All the regedit settings are in place means intune deploy this policy successfully. Please understand that intune just deploy policies, and how these policies work is based on themselves, it is not controlled by intune.
Based on my research, by default, Windows Defender and Defender for Endpoint do not automatically scan removable devices as soon as they are connected to a USB port. Someone has discussed this issue, please refer to the following link:
Hope it will give you some ideas.
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