Blender 2.8 alt-lmb orbit view snapping TL;DR What is this damn thing, and how do I turn it off?

I'm trying to work out a smooth workflow for using the new grease pencil object on an NTrig based convertible laptop.

The first problem with this setup is the lack of a keyboard in tablet mode, which I am working around by using an external keypad (old Nostromo n52, really handy!).

Second problem is that the stylus only has LMB (tip) and RMB (side button) which are not re-programmable, which means there's no MMB for orbiting (emulate three-button doesn't work). Luckily Blender has had alternate view control bindings forever: Alt+LMB to orbit, Ctrl+Alt+LMB to zoom, Shift+ALt+LMB to pan.

Now I have a new problem, there seems to be a new (to me?) feature for view-snapping. It is very hard to search for, and I've found no actual documentation of the feature. Unfortunately the shortcut is Alt-Orbit, regardless of how you orbit. The result is I can't orbit without the view randomly glitching/snapping around.

So the question is: does anyone know what this feature is called? And more importantly how to disable it?
While looking for another setting (Viewport roll) I found this under Preferences > Keymap > 3D View:
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Removing those two entries (clicking the X) allows me to orbit smoothly!