I've had that requested a few times, but unfortunately it'd involve redrawing a large part of several hundred tiles across all of my tilesets - potentially multiple hundreds of hours of work. I'm afraid it simply isn't an economical project, so I've got to stick with the art direction choices I made initially.
I do think the decision was unfortunate and artistic. In 57 years of wargaming flat hex bottoms have been the norm on 90% or more of the maps I have seen. That said, if you have a high mountain peak a point down hexagon gives you a lot more room for a mountain without having it cover half the hex above.
Yeah, you're quite right - it has been people coming from the perspective of old-school wargaming that have a problem with my hex arrangement. And while I've played a few old-style hex games, I'm obviously not from that background so my first thought was toward what was easy to draw for me and looked good in that style.
I have considered drawing a simpler hex terrain style set - possibly lower resolution, definitely simpler rendering - and maybe I'd see about the flat top/bottom for that. It does seem foolish to potentially cannibalize my own sales, but it might be an interesting project (and maybe that's what's most important, at some point).