Length of HT is never meaningless! It's just relative, and I think that's what you're saying. Yeah, you have to take BB height/drop into acct., which I didn't cover. So a Surly Xcheck does have a high BB, with a drop of only 66mm, but let's contrast that with a more racer-ish geometry like the Soma Smoothie (still a heavy, utilitarian bike with eyelets and braze-ons). The Soma has a BB drop of 70mm. Someone might say that's noticeable, but it's only .5cm and really won't effect overall contact points that much.

Xcheck has 40cm fork and a 12.5cm HT on the 56 size. That puts the top at 52.5cm. Soma Smoothie has a 36.5cm fork and a 15.5cm HT which puts you at 52cm top. Your but will be .5cm lower on the Smoothie because of BB drop. Not a big difference, but ultimately the TT is 1cm shorter.