This is not profound info but I never noticed before. Anyway...

I had a batch of 8 TV captures of Futurama captured in a random
mix of 352x480 and 720 x 480.
When I authored these with MF2 I thought there was something wrong
with the files set because there were 2 titlesets.

It put all of one kind in one set and the rest in another. Amazing.
I didn't think the cheapo authoring programs would do multiple title sets.