@Rocco, Thanks for posting in Q&A.
For our issue, I know the app affected are downloaded via their personal Apple account. Based on my research, there's a setting named "Block removing apps". But it only apply to Automated device enrollment (supervised). Please confirm if the affected devices are enrolled with this method? Did we configure this policy for the affected device? Here is a link with the setting for your reference:
However, if the device is not enrolled with this method, I didn't find the setting to block the uninstall behavior. To narrow down the issue, you can install the same app on a not enrolled device or unenroll the device to see if the same phenomenon. If yes, that means the issue is on app side and iOS side.
Based on my research, there's some apps can't be deleted on IOS. You can try the methods in the following link to see if it can be deleted. However, if it persists, I suggest contacting Apple support the get more help.
https://www.igeeksblog.com/cannot-delete-apps-on-iphone-ipad/
Note: Non-Microsoft link, just for the reference.
Please check and try the above information and if there's any update, feel free to let us know.
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