Well, there never was any law that required robots.txt to be honored. Big players like Google do, but I am not aware of any consequences if they wouldnt (of course UNTIL it is then regulated).

Curiously this link seems to show the "Academic" lens. Switching to the "Forums" lens pulls it right up for me.

For me it doesn’t show up in your link with the full article title but with this one it’s the 3rd result or so: https://kagi.com/search?q=remarkable+pro+hands+on+review

I don't think there's anything special; I very often get new-reddit results with no 'site:' qualifier. I can't think of a specific query offhand, but it happens multiple times daily for me.