There are several reasons why I believe that I'm very difficult to hypnotize. It's not just about audio, though that is the hardest one to work around. There are some that I'm unwilling to explain for privacy reasons.
But there are also some that I will explain. I'm a very cautious person, and if you had only shipped the .rpyc files without the .rpy source code, I'd have been very scared of what Hypno-chan would hypnotize me to do. I probably wouldn't have been able to drop into a trance even if I wanted to.
Another is that I'm very prone to fixate on throwaway lines that seem "wrong". For example, a lot of inductions say "twice as deep" or "ten times deeper" or some such, which asks me to quantify trance depth. That would completely ruin it for me.
These are things that a professional hypnotist could easily work around, of course. But a recording made by someone who wasn't customizing it for me likely wouldn't. It's kind of a fluke that Hypno-chan didn't try any of the things that would wreck it for me.