Yes, and since typing is only at compile time, it's also missing some of the extremely convenient pattern matching syntax that I love from Haskell, Rust, Scala, etc....
Despite some downside, I'm a huge fan overall though. I haven't tried ReasonML or ReScript, but compared to bare JS, TypeScript makes frontend programming a lot more enjoyable to me.
I consider ReasonML and ReScript to be effectively dead since they split the community a few times now. I don't know anyone who's actually using either in production, except for their respective sponsors Meta and Bloomberg.
That was my first interpretation as well, and I don't think there's actually any such technological limitation.
But I think what was meant is that typescript's mostly committed to not changing runtime behavior of the JS that remains when you strip the types away, and while I we might disagree with that goal or with its application in this instance, I can at least see the flow of the reasoning and label it a matter of priorities.
Despite some downside, I'm a huge fan overall though. I haven't tried ReasonML or ReScript, but compared to bare JS, TypeScript makes frontend programming a lot more enjoyable to me.