I play the piano for a long time. And I have a clavichord that I tune myself and can tune microtonal to make such tests, which I do.

I can clearly hear different microtone combinations when playing multiple neighbors at the same time on the linked 53 note keyboard.

I'm sure at some point those tones will converge into a single note to human ears, but the fact that a 53-note keyboard exists shows that people can absolutely hear smaller divisions than just the 12 standard notes.