Chibi's fetishes are so revealing, in so many ways. Perhaps the most obvious implication is, of course, how much of a depraved coomer he is. How much do you have to elevate the depravity level to land upon shrinking fetish? It is so abstract and outside the realm of possibility that it basically announces to the world, "I have masturbated to so much weird hentai shit, and had so little actual sex, that I can only get off on fucked up Freudian fantasy shit." And he tells this openly to any teenage girl showing him a modicum of attention. How would this ever succeed with a real person??
Given what we know about Chibi, it just fits so fucking perfectly. Can't get it up for regular sex? Well, Giantess MommyGF can use my whole body, my skeleton will remain hard for my goddess! Lazy and can't satisfy women in general? Make her use you as a dildo, that way she does all the work to get herself off, so you don't have to. Seriously infantile and overwhelmed by the pressures of living as an "adult"? Skip the babyfur roleplay, go straight back to the birth canal with your whole body, trying desperately to climb back into the womb.
There are some really weird kinks out there. However, most of them can actually be performed in actual sex with actual people, not some shit that only exists in the deranged mind of some incel hentai-drawing mangaka. You only get to that point by being a terminal coomer, and any woman that finds out about this will know that on an instinctive level.