Not just that, when I was there (2013-2014), you couldn’t even post a line of code on Stack Overflow or participate in any MOOC with coding assignments without prior approval. (The security folks couldn’t do any CTFs either.) I doubt any of their competitors have such extreme policies (except maybe Apple, who knows).
Apple allows for participating in CTFs, at least under the usual "in your own time, using your own hardware, representing yourself and not the company".
