Since the troll's session was doomed since they didn't do the ecto biology then wouldn't it be the same for Dirk, Jake, Jane, and Roxy's session? Since John already made them.

No. The trolls session needed to be doomed and scratched so that the post-scratch trolls could exist and make the pre-scratch trolls so that they could play the game in the first place.  Whereas John made the kids before hand so they were already made and can still play without having to worry about it.