I tried looking through the changelog and forums with various search terms, but it doesn't look like this is intentional. In tag co-op, unlike before where both players did each spinner, it now picks one person to do the spinner while the other watches. I'm not sure if there is a pattern or not to who gets what spinner but it might be whoever did the last combo? Either that or it's essentially random; I haven't been able to predict it, at least. It can really throw you off when your partner has is significantly better or worse than you at spinning, since the only visual indication it's not your spinner is a dimmed mouse cursor, which is hard to spot, and the sudden odd sensation of the spinner not matching your spin at all.
Perhaps this is related to the spinners not nessecarily having new combos anymore?
Perhaps this is related to the spinners not nessecarily having new combos anymore?