So if my view is over the NSScrollView stack, it gets its -mouseMoved: events just fine, if an instance of that view is over a WKWebView (with innocuous static content), it gets weird hiccups, where the events drop out for a second or two occasionally. (Trying to recreate in a stand-alone app the thing where the scroll view drag is getting interrupted by other views.)

Searched for myself on YouTube. Got a whole bunch of ads promising to reveal my personal information, okay, but then also suggested that it could "Find Old Girlfriends" and "Find Old Boyfriends", and now I'm curious about who it thinks are my old girlfriends, and definitely intrigued by who it thinks are my old boyfriends...