Not revealing his methods, I am going to say he is simply a liar. Matt Clarke is correct in stating that their osmoregulatory systems are not designed to handle the high levels of salinity. Four months is too short to attempt a publication that he has acclimated a FW fish successfully to SW (not counting the ones that do adapt to SW as they grow).
wouldn't be surprised that it lived some time in SW, as many cichlids can do that (Mayans, Black belts, a few tilapias) by living in marine conditions for some time...but hardly a good long term thing for those blood p's