Is there a way to turn off field capturing and switch to frame capturing?
Not than I can see. In VirtualDub there is "Swap fields" but in looking that up and trying it, that is not of any help (it really screws the captures up, a fix for something that's not broken with my particular capping set-up). I did more searching around the internet just now and still found no one else having talked about this particular bizarreness. 
At least my captures all look great and beautiful, and for that I am thankful. 
I could just discard ~half my caps, do only an averaging of the "shifted down one line" versions I guess, but the learning side of me would really like to know what is behind this weirdness rather than give up and do simply what works in a state of ignorance. (<-not to mention the time of having to do up to 10 or 11 captures instead of a straight 4 or 5 for everything I wanted to do averaging on!)I did more tests to make sure I wasn't imagining things, and the same still holds. To risk being repititious (just hoping I'm doing helpful clarifying), doing a slew of caps of one scene will result in two "categories", the interlacing starting point (and flowing 3-2 style) at a different point between the two but consistent within each, and one of the two varients is lowered one scanline compared to the other (i.e., all of the captures that are in the "shifted down one frame" category will have an identical interlace pattern throughout the footage and are completely "average-able" barring an auto-inserted duplicate frame every few minutes).
Thanks again for the replies and trying to help me look into this Arnie.d.