I pretty much ignore seattube measurements when I look at MTBs.
I have a 15.5" 1996 Mongoose IBOC with a 130mm stem, 560mm TT
And a 19" 1997 KHS Comp with a 100mm stem, 600mm TT.
I love them both.
A slightly shorter stem on the KHS would be nice, if I see an 80 or 90 stem for cheep...