I'm sure its probably something simple like that, going by the track record.
I actually started looking at the spells properly for the first time (ie looking at the data, not just testing in game), there is all sorts of weird stuff going on. Even the simple 1st level spell 'Shield' doesn't seem to have an AC mod effect that I can find, it is just 2 animations and a sound...
I only got so far into doing that when I couldn't help thinking 'should i just override some of this crap with stuff that actually works in the other games, so at least there is something rather than nothing?'. Would that be something helpful?
I mean pragmatically, I just want to be able to play the game, I am much less interested in what weird stuff Black Isle were smoking at the time they made it. Much as it would be nice to have a 99% accurate recreation of the original game, it would also be nice to have something relatively functional in the meantime, even if it would ultimately be destined for the chopping block...
Plus there is that voice in the back of my mind that says 'making PST behave like the other games could only be an improvement'... I mean I love Torment the game, but I also hate parts of it... I was never a fan of the whole 'cast a spell, wait five minutes for it to play out on the screen before you can do anything else' way of RPG making. That's the beauty of BG/IWD, you can stop at any time, but you can still have fast paced carnage if you can choreograph it well enough. Torment doesn't have that, it just somehow makes the up for the absence of it in other ways. I think at the time they probably just lacked confidence in how well the realtime w/ pause system was going to work, so didn't run with it.