I've noticed that even if their animations were sped up it probably wouldn't make that big of a difference because the AI often takes time to calculate exactly what it should do.
And then I usually laugh because after sitting there doing nothing for 4 seconds it often does something incredibly stupid.
Also as the original X-com is one of my favorite games and I've played it far too much I can attest to the movement settings in the game. You could even set it so high that all movement and shots happened basically instantly.
