The trend in the bike industry is to have a longer dropper post with a shorter seat tube. For example the ibis Ripley and Ripmo, two of the best selling bikes in the industry, have ST lengths of 418 and 432mm respectively. It allows for more customization via different length dropper post and is much nicer as you can move the seat way out of the way when you are descending. With dropper post reaching lengths of 240mm, it shouldn’t be a problem accommodating longer legged riders. Additionally, droppers are starting to have shorter and shorter insertion lengths, which can make up somewhat for a short frame insertion length. If this seller wants to sell the most amount of frames, he should try to lower the seat tube length. As it is, it will deter buyers looking for a frame with modern geometry.
well the Ibis bikes don't have a shock running through the seat tube either. have the seat post insertion lengths been posted yet? I have a 180mm dropper on LCFS947 and I have 90mm of the non-dropper post sticking out of the frame. Not once have I thought that I needed a longer dropper. I am guessing they had to go with the choices they did because of the shock placement and needing to have a specific amount of insertion length.
Also trends change, wait a few years and this may be the new "in" frame design.