I'm on a MacBook Pro with macOS Big Sur, and on both the laptop trackpad
and with my plugged in USB mouse, the wheel or 2-finger up/down on
trackpad, is reported to Emacs when in terminal as mouse-4 and mouse-5.
That means that scroll doesn't work in Terminal.app or in iTerm2 on MAC,
since mouse-4 and mouse-5 are not bound.

In the GUI Mac it works, because it gets reported as wheel-up and
wheel-down.

My thought is maybe here
https://github.com/emacs-mirror/emacs/blob/master/lisp/mwheel.el#L54
there should be an additional check for if its running with a
window-system or not?


In GNU Emacs 27.2 (build 1, x86_64-apple-darwin18.7.0, NS appkit-1671.60
Version 10.14.6 (Build 18G95))
of 2021-03-27 built on builder10-14.porkrind.org
Windowing system distributor 'Apple', version 10.3.2022
System Description:  macOS 11.3.1