Imo, Rust makes a very good second language for someone who first learned Javascript or Ruby — and someone who used those languages primarily for web dev may never have needed to learn about bit shifts
Also, JavaScript's handling of numbers is so weird that it's one of those things that comes up just by virtue of its weirdness. For that reason I'd expect a JS programmer at least have come across but operations.
(edit - I take the original post as a joke too, and that the humour is derived from the juxtaposition)
I know I've seen examples at least as odd as this in the past in languages I'm familiar with -- where, say, the developer was really good with LINQ or something and made five calls instead of just accessing an array by index -- that were meant "intentionally", but were bizarre to someone not sitting in their brain at that moment.
I hadn't, however, thought about either of the points you mentioned.
You're quite the detective. :)