It is a valid concern if you send an entire list of confidential data and ask it to transform that list. However if you ask ChatGPT some questions about coding in general it's no different than searching online.
This comes down to whether you trust your whole organization to act be educated about these issues and be good at judging what's ok.
At the size of Samsung that's just an impossible move, and it's easier to blanket ban a problematic service and have employee request exceptions justifying their use case.
BTW I've been in companies that blanket ban posting stuff online, and got posts security reviewed when asking help on vendor community forums. That's totally a thing.