It’s true. In a way, anyway. It would actually be more accurate to say it was true eons ago, although yes, wild salandit do indeed display this behavior today. Still, even if you removed such a salandit from contact with a female and fed him well, he still wouldn’t evolve.
This is because of adaptational evolution. While female salandit retained their ability to evolve (so they can get stronger and lay and protect their eggs on their own), male salandit adapted towards a form that would allow them to survive while still devoting the majority of their available food to females, who need the energy more. Eventually, males simply lost their ability to evolve altogether, as their salandit forms were better suited to survive such an arrangement.
It’s actually a very fascinating subject, and it’s been the subject of thorough discussion in the scientific community since salandit’s discovery.