If you wanted to get technical, FFX could have been part of Spira as well rather than the whole thing, from the sheer fact you weren't mechanically able to fly off the north edge of the map and end up at the south edge.
(lol)
My point being 'the entire world' in most classic JRPGs were not physically possible constructs.
As stated, I don't expect being able to traverse entire world literally to the scale... Basically, I don't want there to be blanks in the world because they couldn't fit it. If there are like 2 more continents with their own empires on them, let me visit town from each. I want to be exposed to every single culture, architecture, yada yada...
Allow me to explain myself a little better. Imagine there's a continent to the east, that has an entire country of magical Moogles that fly on fairy dragons and live in trees. In old JRPGs, even if it's just one town, you'd see that.
After I completed Final Fantasy 9, I didn't see every single town that exists in that universe, obviously, but I've seen every single country, culture, everything that world had to offer, all it's secrets, all races and species that inhabited it... ALL of them I met and saw at least a little bit off. That world had nothing left that I didn't see.
That's what I prefer my JRPG worlds to be like. I don't need them to make an entire moogle continent explorable, but if it exists I get some basic exposure to it and know basic idea of their culture, architecture...
It's weird and very emotionally based rationale, but that's the one I have about JRPG worlds. if you created a magical world, show me at least a tourist bus tour of IT'S ENITRETY.