Is there a particular reason why swinging the sword from below to up feels strange?
the reason is pretty simple, you don't use a sword that way. a swing like that it's something very uncommon to do. I can agree with the design decision to have X weapon not hit above etc, but the classic sword swing, it's an up /down move. A stab/point/Dmc stinger it's a back/forward move. So in the end it's just a problem of skin for said weapon.
Cursed World is the first area of the game, it is supposed to be a "twisted forest" with labyrinthic design, nonsense geometry and risky room layouts
It's your game, you can do what you want. Imo, this is pure nonsense. The first area of the game, be ragebait/kaizo or not, is to be the easiest zone of the game. A place where you get introduced to its mechanics with a certain degree of safety. You can't say to me that your first area is very hard, labyrinthian and full nonsense; but the second area is chill an more normal. Everyone will quit the game before getting there, because the rational thinking will be "if this is the beginning, i can't imagine wtf will come next".
There can be exceptions of course, but they are mostly story related. You start a prologue from the end of the story; you start with a powerful pg from the past/future etc etc
It's your game, you can do what you want.
ED: lemme add that, empirically you can do whatever you want; the problem is to make a player care, and stick around till the end