UPDATE:
X-COM arrived today, in physical form. It has no ESRB ratings on it, or any ratings at all for that matter. Here is the back.
I played through the first two missions and it seemed fine.
Of note: It came with a DLC code, which doesn't seem to work.
Also, I tried for about 20 seconds to play multiplayer, but it didn't matchmake. I might have just been impatient. Not sure yet.