I'll take a stab at it and mention... it sounds like you did not learn traditional typing (home row and all that). I do the same thing you do, and I find I can adapt quickly to impairment of any of my fingers without any thought. Those that I know who learned "proper" typing seem to have a harder time with that.
I should mention that typing doesn't really bother my hands at all, though I do get some forearm fatigue after an extended period of typing. What really bothers my hand(s) are mice. I switch hands, but I still end up with fatigue/aches when using the damn things.