Leareth thinks that– Leareth stops and actually thinks about it.
He...does expect he's better than most humans at, just, deciding to be a certain shape, having his mind do the motions he wants it to do and not the ones he doesn't - he suspects he's done that before but in the direction of not wanting sex, back in Velgarth where the thing he might actually want, a close relationship with a trusted ally who would still be there a thousand years later, wasn't something he could have even in theory.
He's pretty sure he couldn't change it arbitrarily even if it were convenient - probably if Maitimo belonged to a species that looked very ugly to human sensibilities, instead of very aesthetically beautiful the way most Quendi do, he wouldn't have had anything to lean into there. Or - if he were starting from zero, instead of starting from a base of more closeness and intimacy and fondness than he's had with anyone in the last five hundred years, where he already felt safer than anywhere else in Maitimo's arms - he feels like that already is the core thing that would underly him wanting sex with someone too.
He's done some amount of nudging emotions, though a lot of it was just bothering to notice that 'wanting to touch Maitimo's hair', say, was even a possibility, rather than trying to turn 'not wanting' into 'wanting', he can't generally make that work as a primitive motion. Leaning into an angle he already has usually just works, though, and he's never considered it a problem or a bad thing to do? His mind is frustratingly full of obstacles and traps and pitfalls right now, which - okay, he can see why Melody thought this was a dubious plan and he would just hurt himself, he's probably miscalibrated about what he can and can't do right now.
He's not sure what the conclusion is here - whether the actual thought process he had is one Maitimo would consider 'wanting it' or 'not wanting it'. So he leaves it hanging between them, for Maitimo to decide for himself.