This is a simple script modification that adds one new condition with an early exit to the elemental whip script event that is responsible for casting spells and draining magicka.

The original mod's script for casting spells tied to the three elemental whips doesn't exit the conditional early if the player is not wielding a whip, and, in fact, jumps to checking and draining magicka if a left/right power attack is detected which leads to magicka being drained while power attacking with some weapons, most notably all greatswords and AA's very own pikes (which are kind of greatswords too). The script simply exits the function early if the player is not wielding one of the three elemental whips.

I haven't the faintest idea as to why it only drains magicka with greatswords and not other 2H or 1H weapons. Maybe the animation event is different, or IDK.

The script overall appears to be in a very... strange state, and testing with the original mod only I couldn't get the whip spells to work anyway. This change shouldn't break them if they do somehow work, but I'm not inclined to test further since I will likely be playing with the no whips version of the mod, and I recommend you do the same. If you have noticed this issue midgame you can either install this script replacement if you want to preserve the presumed functionality for the elemental whips, or you can simply delete/hide the NA_Uni_Whips.pex script.

Modified source included.