I have video of each of these, except Clemmont and they ALL finish with the throwing shoulder and arm completely followed through and the hips rotated fully as well. I would not categorize this as a "good fielding position". I agree 100% with chinmusic in that being able to field a ball after the pitch has been completed with no compromise is a BONUS.
I've not recommended that one should "fall off to first base". That would be taking my comments too far.
Again, I didn't mention anything about an off balance situation or falling off to first. Quoting something I did not say doesn't negate what I did say.
A pitcher must flex forward with the trunk while rotating the shoulders and do this while on the opposite foot only. This mandates a lean to that side but not necessarily a "fall to first base". My point is that, if you finish your pitch into a nice flat back finish with the throwing hand/arm following through to an area to the outside of the plant leg and the shoulder "buried", you will not automatically be in a "good fielding position". One should not compromise the pitch by attempting to be so linear, toward the plate, that the fundamental purpose of being out there is lessened. Now, that doesn't mean that one should go from one extreme to the other either and concentrate on rotation only.
Pitch first, completely, then field the position. Bonus.