My question is, are the seat- and headtube angles the same? Sometimes different sizes of the same frame have different geoetry. In order to get similar ride characteristics and still get toe clearance, wheel clearance, and such, larger frames will be more upright ... wjoch could account for the larger head tube.

I am getting tired of saying this ... but I got a dollar-store drawing kit and sketched out the actual geometry of the frame w\I was looking at, so I could draw in different spacer stacks, stems, and seat posts.

If you jack up the seat on a smaller frame with a slacker angle, it moves way back, so seat to bar might be longer than on a frame with steeper head- and seat tubes. Add that taller head tube and you might be looking at a slammed short flat stem instead of spacers and a long up-angled stem to get the same bat position relative to the seat ... and the bike my handle differently and balance differently.