A Samsung employee in one of the overseas research centers. I'm not sure about this at all. The most that is restricted is one cannot shoot pictures - either camera lens gets a cover (paper sticker) or the camera is blocked using MDM.

This is practice in many companies and I hear at Apple it is even more restrictive at certain places.

Not able to use phone I never heard or experienced. We regularly test out apps in phone, test out devices (non test ones), we test competition ones, etc. And when one can get on a Zoom or Team's call, what use is restricting phone usage.