"""""""""""But it's just not really practical for me to focus on keeping modeling operation failures around for a kind of "side effect" like that..."""""""""""""""

But it wasn't really a failure. I mean, if the curves are not planar, then the extrude is an open surface. That's just the way I understand MoI.

The fact that the original 2d geometry is out by only .000000000000000001 is more incidental to the fact that it's "out"... For me.

Small little "rotations" in geometry will produce errors in operations further down the road in my model, that will make it much harder to get back and fix. Things like "How the heck did those 2 surface seams get just far enough off to produce a teeny tiny little fragmented sliver that causes all fillets and further Booleans to fail in that area, 3 days after I originally made that mistake... Kind of thing.

I understand what your saying, I just wanted to convey the importance to me, to you, about keeping an ability to catch those..... :)