I haven’t heard I’ll be feminine for the right man but I’ve heard submissive. Because how are you going to be submissive if you’re single? Or if the man isn’t the right one?
I think the equivalent would be a man saying he’ll be a provider for the right woman. Because you can’t do that with everyone and you can’t do while single.
but as for the question I would be turned off by a man saying he would only be masculine for the right woman because how can you turn that on and off? Why would you want to? I assume a man would be thrown off if a woman said that she’s only feminine sometimes too.