Magic Mouse successfully connected to iPad Pro but won’t scroll

I’ve just updated my iPad Pro 12.9” (2018) to iPad OS 13.4, which enables mouse and trackpad support. I successfully connected a Magic Mouse, and the pointer, clicking, etc all works as expected. BUT, the mouse won’t scroll for some reason.

I’ve tried with two separate Magic Mouse devices (which both work successfully with a MacBook Pro, so the mice are fully functional) and after unpairing them from my Mac, and then pairing them with iPad Pro, neither can scroll in Safari, Mail, etc.

Is anyone else seeing this? Is there perhaps a bug in this new feature, or a setting I’ve overlooked?