Wow isn't cross platform.
Doesn't mean it couldn't have been. Frankly, I wish FFXI and FFXIV weren't either because releasing MMOs on consolse is stupid.

Zone lines are better in FFXIV's situation. We already have zone lines, they are just wearing a disguise.
Yes. That disguise is the lines aren't visible at all, and the user doesn't notice unless they're conciously thinking about it. That's the whole point of seamless transitions. They could have implemented them better in this game, but any seamless transition > loading screen. I'd rather have loading not directly interrupt anything, even if that means you're walking through a short tunnel. That's still better than a fade to black.

Console only single player RPGs don't need to load a billion different equipment configurations for every human player in the zone you are loading into
FFXIV isn't a console only single player RPG. Your point doesn't make any sense.