@Q34Guy,Thanks for posting in Q&A.
Based on my research, the Optional diagnostic data (Full) of Diagnostic data settings is support view Browsing history
To clarify this issue, please check the following.
1.Please check whether your device meet the requirements.
2.Could you share the policy status in Intune portal?
3.Please try to disable Diagnostic Data Viewer data and re-enable, restart the device then re-collect the diagnostic data to view it to check whether the issue can be fixed.
If there is any update, feel free to contact me.
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