Yes, I fail to understand the difference between speciation and subspeciation. It stands to reason that if beings change to develop into creatures that can better exist in an environment, then given enough time they will develop into a new species. What is the mechanism whereby creatures evolve, but stop just short of evolving into a new species?
I don’t think it works - if you accept subspeciation then speciation follows logically.
Clearly, they reach a stage of development and enlightened understanding in which they simply refuse to accept evolution.