Never played MoP but this is almost like most MMORPGs, linear story, you go from guy to guy and from zone to another, and you end up somewhere where all max leveld guys are, somekind of city probably, but zones are alot larger than in normal MMORPG games, yeah, you need to go to explore to find more quest, btw, very first dungeon is only found by exploring the area, no-one tells you where its, player find it out of sudden while he wander around the zone.
Btw, that guy in the video is obvious troll. I wouldnt click any of those links, hes probably haxor.
No I think it won't be at all liner. There will be hubs, however, those hubs are jumping points rather then a central quest location. So you will get a quest at said hub which will lead you towards an area in which other options are available. So you might get a standard sort of go kill X spider’s type of quest. However, on the way or as part of the general quest itself multiple other branching options will emerge.
Also, the guy on the video is Jesse Cox a highly respected video game blogger, voice, not sure what the proper title would be, however, I highly doubt he is trolling. If he said he played an Alpha version I would it be a pretty safe bet he played an Alpha version.