I would argue that Typescript and React or Vue would have been a better solution for the customer. Yes, Elm might be better in some aspects, but I could name quite a few benefits for Typescript as well.
I think the technical reasoning is okayish, but from a business perspective I don't think the customer made a good choice.
I think the technical reasoning is okayish, but from a business perspective I don't think the customer made a good choice.