The space from handlebar to saddle is adjustable but UCI rules are putting a limit to this (Saddle position and length of aero Bars are regulated by UCI).None of this makes any sense nor is there a different between road and TT.
Why would a long torso matter? It's horizontal.
Why would long arms matter? You just adjust your touch points.
The space from saddle to handlebar is adjustable based on frame size and stem length.
If Ganna hasn't bothered to optimize his position on a road bike and Evenepoel has, that has nothing to do with their heights.
So a taller rider might have to be more upright to fit the UCI rules.
you would be right if there where no UCI rules and you could still use the superman position that boardman used but with the UCI rules a taller rider might be more "crunched" on the bike.