A quick thought: this seems more correct to replace the mouse/pen specific lines with:
"No change in active buttons state => 0"

Pen moved while hovering with no buttons pressed

Note that "moved" here includes the cases when the "footprint" of the pen is unmoved: e.g. a change in twist. I think the pen still must move physically to generate an event, so this is fine.

Do we need a note?

I think it's fine to treat that as implied.