@Brian Liu, Thanks for posting in Q&A. For our issue, to clarify if the issue is with Intune or Teams. You can choose one unenrolled device to test to confirm.
Meanwhile, in Intune, we mainly focus on protect company user data. But from your description, it seems the issue occurs on personal team account to send video to external users. Based on my experience, it is not set in Intune.
After checking in Device restriction policy, app configurator policy, I don't find such setting either.
https://zcusa.951200.xyz/en-us/mem/intune/apps/app-configuration-policies-overview
https://zcusa.951200.xyz/en-us/mem/intune/apps/manage-microsoft-teams
But I find a link describe restricting file sharing in Teams with external user. Not sure if is related with our issue. You can contact Teams support to double confirm on this.
Hope the above information can help.
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