If the story doesn't make sense, that usually means we haven't heard the whole story.
1. don't want to potentially lose revenue
2. don't want to dilute their brand
3. don't want any liability associated with an employee doing work outside of their officially sanctioned capacity
4. don't want to culturally set an acceptable level of noncompliance with procedure even if the above violations aren't egregious.
Insurance is very concerned about claims resulting from off the clock / third party work related to day time work. So if you are a doctor working in a practice group, and then do freelance work, that is going to absolutely freak an insurance carrier out.
Security - people don't realize that a lot of stuff on-premise / on-network is tracked and logged. So if you "help" someone out off-site / off work people get nervous. T-mobile employee doing a sim swap with customer in store on video - sure. T-mobile employee logging in off hours to do a sim swap - maybe sketchier even if they are "helping a friend".