I thought it was a bug when I read it, then tried it myself. Slime Girl Smoothies? A game by that name is the first result. In Heat? Likewise. Fear and Hunger doesn't, but I have a suspicion that the game used to be on itch.io and was removed. Are you searching with NSFW mode disabled, by any chance?
Viewing post in Why does itch.io search suck so bad?
It is a mature horror game and does show up as first result if you search for fear hunger or fear & hunger (for me). With fear and hunger, it shows up lower (or not - search is random and truncated after all).
So, yeah, mature browsing not enabled issue. Plus, the search knows the difference between & and and.