Rewriting over a million lines of code in a statically typed language coming from one likely as riddled with type errors as this codebase is is unlikely to be productive. They're making the best of a terrible situation.

I also think that if they want to use types the correct approach is to apply a tool like this as a stop-gap but write new components going forward and bug fixes/feature re-writes in a language that supports types "properly" (i.e. in the way they seem to want, that is static types checked at compile time).

I think tools like this are great for companies in situations like this. I don't think they're good to use from the outset: the team should just use an actually statically typed language instead.