Yea…. well there are far too many versions of the same stories and each depiction is different. Sometimes Eros is a primordial god, and sometimes he's the son of Aphrodite. Sometimes he's an adult male with a blindfold, and sometimes he's a putti angel.
Though what I find more interesting is that Mentaiko only seemed to address half of Priapus's 'qualities'. The reason he has a 'permanent erection' is because Hera (Zeus's wife) cursed him before he was born (in the renditions where his mother is also Aphrodite, as punishment for a snub or something… you'd think Hera'd be used to it though… because it seems to happen quite often) cursed with ugliness, a permanent erection… and ironically, impotence. Meaning he can't actually keep it up when needs sex.
Though that could also make a neat twist. Maybe Priapus could fall in love with a human and not be able to have sex with him because he actually has feelings for the human….. and Eros could be the one who made him fall in love to teach him a lesson…. that'd actually be pretty interesting to read…..