This is a splendid example of the kind of thing I let mentees discover on their own, when it actually starts to matter in what they're doing, rather than burden them with right up front. If binding is an uncommonly encountered concept, interning is a practically unheard-of one, and it would be a severe disservice to explain it, and copy-on-write, at the same time as everything else I'm asking someone new to the language, and often new to programming entirely, to follow.

You're right that the description I gave is fundamentally a false one. But it is a harmless, and an extremely useful, lie.

(In any case, you're underplaying your hand here. If you're going to get deep into the weeds on how Javascript values really work, why leave out implicit autoboxing?)