I mean, it's an unconfigurable, unenumerable but writable property that mostly assumes you're only writing integers into it, but allows you to write anything whatsoever into it and then observe that write going through. If you were to define RegExp today, I would assume you'd use a setter kind of system that coerces to integer during writing instead of like it works now where coercion happens when the value gets used.

I definitely think it's silly :)