Official E3 FF7R trailer description https://www.youtube.com/watch?v=pCJZg7pVtiI&t=1s
As i've stated 100x, they're not hiding this information, it's everywhere.
Literally does not matter. Schmucks will still walk into Wal-mart, swing by the game aisle, see the box-art and buy the game on nostalgia, being none the wiser. I worked in the electronics section at target for a few months & believe me, most consumers I interacted with are that dumb.
There isn't a good reason to not add part 1 to it, other than to deceive people about the actual contents of the game. The only reason people have seem to come up with to not add a subtitle is, "well it isn't absolutely necessary." I mean sure, technically, but that's a pretty shit reason to deceive any # of customers.
Edit: only other reason I see people saying is to put it on the back of the box... you know, the back of the box you can't see when you go to many stores because they're locked behind a glass window with only the front facing out...