Seems like unless this wrapper is refactored to use a different prefix library, rails applications are looking at a forced conversion from asset pipeline to webpacker, just to use babel? Or am I missing something?

I don't know or particularly care. The JavaScript / "asset management" crowd seem to think up new, even more complicated ways to do simple things every day of the week; all I know is that Bootstrap started spewing warnings because it depends on Autoprefixer, which is now end-of-life.

It's Bootstrap pulling in the dependency, not our application. So I don't care what it uses instead; it just can't keep using a gem that's now been killed off.