I’m not questioning typed JS, 100% behind that, we regrettably use flow, partly because React Native Typescript support wasn’t great (so I am told).
I guess I should have asked if FB recommended TS over flow nowadays
VSCode is also written in Typescript. I believe the teams work closely to ensure that new versions of TS are supported right away, and features are added to take advantage of them.
But it is another tool for large codebases that requires more work, like tests. If it's a small web project, it's probably overkill.