Top tube is how you want to size these. The seat tube (not seat post) is normally much shorter in modern frames (track and road these days) because people want a lower headtube for TT bars and low sprint positions. You simply buy a longer seat post (this is the part that inserts into the seat tube) if you need your saddle to be higher. Your reach length (top tube + stem length + bar length) is much less adjustable than seat height.
Edit: 700 Wheel nailed it above. You will not see maximum seat height listed as a frame dimension.