The point is that they saw fit to reveal here.I think a lot of people have overstated the VGA/X's importance. Skyrim was the sequel to Oblivion and had hella commercials and marketing...I'm not sure the VGA helped that much. TLOU was from ND and also was marketed heavily and was praised loudly by all who played it and the press.
I think that has a lot more to do with their success than anything.
I'm not saying it wouldn't help to say show off X here because it would be great IMO, but lets not act like the VGA's are some e3 level stuff because it's not.