And every qbrt app is the same way. If there are two apps 'one' and 'two' written as node modules, and both have qbrt x.x.x in their dependencies, then installing both will leave you with two identical but independent runtimes. There's no sharing going on.

A runtime that can't run the app it's supposed to (because of breaking changes across runtime versions) is also not a very useful runtime, shared or not.

How important is binary size for desktop apps, though?