This logic doesn't seem that simple and can also be inverted relatively easily: if pure animation viewer approaches were more profitable then wouldn't the majority of adult games adopt this model?
Realistically both versions of this argument are dumb as they presume that porn game studios form a completely efficient market where a majority of actors have perfect information, are following a money motive and have the capacity to execute a coherent strategy. I haven't seen much evidence that any of this is true.
In reality most porn devs are winging it by the seat of their pants. They might have a good idea for a project but it's limited by funding, some might not be in it for the money, most seem unlikely to conduct thorough market research and some of them (and I'm including Helius here) are severely limited by ability.
I think if you want to find a proxy for what users want the best point would be looking at the most popular games, and those almost universally seem to have some kind of gameplay loop.
