If you are using TwbT, though, you bypass pretty much the only reason anyone would want to use non-square tiles: To make text not seem "squished" vertically to fit into a square tile.
Can't use twbt in Adventurer mode without running the risk of crashing any time you enter travel mode.
Can't get tiles larger than 24x24 with a 1920x1080 screen without twbt zooming options, but 24x36 fits perfectly and stays that size properly. I would actually use square sets more often if twbt was viable in adventurer mode, though I just prefer the aesthetic of nonSquare ones more now.
TwbT text is a different tileset, so you're making what is supposed to be equidistant tile lengths different apparent lengths (and screwing up diagonals) without it's only real benefit.
TwbT is spectacularly great when it works, it's just that it's really unreliable right now.
I honestly wouldn't even use it with a map/text set much these days, just for the multilevel and stuff like item overrides.
In his defense, when I used TwbT on that rare occasion I liked to keep the graphics the same as the font (or something along those lines, it has been a while). I just put in my tileset for both. The only thing I really used it for was that excellent top down view through all the z-levels. It makes just about any tileset look 10 times better. Even mine! And though I was not really using TwbT to its full potential, it was a nice visual boost without sacrificing the nostalgia of using/reading an ascii tileset.
Aaaaand even though I believe square tilesets are superior in every way I can understand if someone else might want to use TwbT with something non-square.
Well, they're better for doing diagonal wall connections, but that's about it.