So I don't think there's actually enough benefit to split those two apart.
Now I want to do this: just add a meta info (basically a bool field) to the ArrayExpr struct, so on later stages we could tell if that's an ArrayExpr of an ARRAY or of an IN list. Plus to add ignoring updating Jumble for expression subtree within IN-list array.
If that approach doesn't seem too bad to anyone, I would like to go forward and submit a patch – it seems pretty straightforward to implement that.
So what would this do for someone who explicitly writes:
