This change is now merged and is included in currently nightlies. (link: how to use a Scala nightly)
Eugene Yokota’s PR flipped the switch, but it was possible to do so after years of bugfixes and performance improvements to range positions made by assorted people.
Metals (and other semanticdb-based tooling) requires range positions, so lots of people have already had them enabled in their daily work. That, and a green community build run, gives us reasonable confidence that they are robust and fast enough to be enabled by default.
Regardless, posting this here hoping folks will test a nightly, especially tooling authors who think they change might impact them.