It is not absurd to have 4 provinces, TP had 6 themed proper areas (forest, mines, lakebed, desert, mountain, sky). But each of these SS provinces with its respective dungeons are MUCH denser/longer than TP's to beat (that all of them had almost no foreplay), that way SS 4 provinces at least would even out TP's regions. The sad thing is that would had much less variation than TP, only 4 themes, and 3 of them spoiled.
But only 3? And all 3 of them spoiled already? That's absurd, to get worst that would shrink down the Sky size along with it. Let's wait and hope, but don't expect to have any extra area revealed before the game release, if there's more, they won't show us (of course there is more, but i'm talking about proper provinces/distinct areas, beside interlude areas and the final dungeon).