The theory in the book was that it was the siphon effect that made it much more difficult for cultivators after the Genetic Mutation Realm to activate a new genetic ability chain. They might have to put in three or even five times the effort compared to when they were at the Genetic Liberation Realm to activate the new genetic ability chain.
Therefore, those cultivators who wanted to strengthen themselves would only break through when they had unlocked enough genetic ability chains or formed their own combat system.
The choice was: should Xu Tui continue to train his foundation in the Genetic Liberation Realm? Or should he use the directional genetic mutation elixir to reach the Genetic Mutation Realm and quickly increase his strength?