Would it be better to flip this alias? penis is used over cock in every other situation. I feel it would keep things more uniformed.

There's almost nowhere on the Internet I can find using Google where the fetish is referred to as "penis transformation". Searching for it mainly shows e621 because of the alias. I think it's better to keep calling it what the rest of the world does.

I also think it could maybe be confused with someone's penis transforming in to something if people don't recognize the term, and can't find a definition for it.

There's also other existing, more common example of non-uniform terms: pussy/male and cuntboy, penis/female and dickgirl, etc. Calling cuntboys "pussy_males" for consistency would be a bad idea for the same reasons.