Good to know, that's what I was expecting. I'll have to give the Cat a spin! Also, thanks for this article and the Jef Raskin one - I thoroughly enjoyed them and their depth. I was in the middle of reading the book version of folklore.org (Revolution in the Valley) and these were a pleasant surprise.
In Superkey, all of the matches are highlighted yellow, and the selected one is highlighted green with a line to it from the text field. You can keep typing to narrow down the match, or you can navigate matches using the arrow keys (and optionally, cycle through them with the semicolon key, which is what I use). There's a screenshot at https://superkey.app.
For the Canon Cat, I'm actually not sure as I've only watched videos of this functionality there.
At the moment the Accessibility API results are limited to the frontmost window; it's on my todo list to expand this to additional windows and displays. Also, the green line will only be drawn on results on the main display - another item I plan on fixing.