A baritone has one advantage: it is so large that the relative precision with which it is constructed is high in relation to the frequencies that it puts out so being out a half millimeter on a valve seat will not immediately have a huge effect.

Also: have you ever thought about how undefined the frequency of a sax really is? The seal is a large, round flap that drops down over a circular hole with a raised edge. Even if you open it fast there is a gradient there and no matter what you do the hole itself is shaped to practically guarantee a different frequency response for every part of its circumference! It's a miracle it works at all (same goes for flute, oboe and clarinet).