I don't think he gave a specific comment on the size of the other areas saying they're linear or anything, just saying zone/area based like he did in general should be enough to know the world is just that: zones (Dragon Quest, Xenoblade, FF14), not on extreme or the other. At least to Dengeki he just clarified that while it's not a open world, they have at least 4 fields that are that expansive size and give that feel. He also suggested you can come back to clear side content after the main story and there's plenty to do whenever.
The other thing was when they conducted their global user research, very few actually cited an open world as a main FF desire. Demand mainly varied from good story, good graphics, and interesting gameplay. He even brought up FF15 attempted an open world to some degree, but his team thinks before anything like that, the story of FF should be the focal point. In general, he didn't want the team to force themselves to make one or feel pressure to.