Tthe absolute test devices (and thus real devices) have button scrolling available but it's not hooked up anywhere in the code path. Drop this.
https://lists.freedesktop.org/archives/wayland-devel/2017-February/033166.html
commit c225c0592c4b3b61a01b6227f293b7fb853d5dbf Author: Peter Hutterer <peter.hutterer@who-t.net> Date: Mon Feb 20 16:29:02 2017 +1000 evdev: don't provide button scrolling on absolute pointer devices
Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.