The changes were more than just a slight, cosmetic adjustment. It was almost a redesign than just an 'update'.
Just google Deathclaw and check out the images.
The originals are much more reptilian and has a hunched back. On the other hand,Tactics version is much more mammalian in terms of having fur, upright stance and other humanoid features.
EDIT: Overall, Tactics was a temporary fix in our desire for a proper sequel. A great deal of its flaws was acceptable for me as it did not try to play itself off as part of the originals. Instead, we got a hybrid spinoff of Fallout meets Jagged Alliance.