Micchy's probably still extremely confused, but I imagine obeying (at least superficially) that tone of voice is ingrained enough that he wouldn't question it. Or maybe since the only person who used it is dead, he figures the fruit isn't real either. Or that obeying his hallucination brother is the least he can do.

That's true, hiding the garden and preventing the growth of fruit also nicely keeps humans from trying to eat them.