I strongly suspect that what's going on with "people who talk to children like they're adults" is that they talk to children like they're people.

Anecdote: sure works for me. I have zero personal interest in sticker dolly books or drawing pictures of dinosaurs, but my 4yo sure does and she lights up when I participate in her projects in a way that takes her interests seriously. We are blatantly and consciously encouraging her interests in art and music, and she's getting commendations at school for it. She's even allowed to touch mum's Wacom graphics tablet ...