That's because that variant is written for PARASITIC tails with their own impulses and drives and not for a tail under your control:
The parasitic tube’s peristaltic gyrations are so much more powerful than your real vagina" + (pc.hasVaginas() ? "s" : "") + ", and now that you’ve stopped trying to suppress its urges, they’ve somehow supplanted your own.
As the creator of the cunt snake transformation, I try to include a scene for them in almost every character or encounter I touch. I would be thrilled if the authors of non-parasite tail transformations endeavored to provide more options for them.