Indeed, though from a conversation with the author, it's only implemented for a subset of what was described in the post, specifically only for data construction. (Conversation: https://twitter.com/let_def/status/1485313834764095488)
Is this similar to Racket's stack replacement infinite tail recursion mechanism?
Isn't that just standard TCO (scheme, unusually, mandates this in the standard)?
No, Racket's work for non tail call recursion too. The standard recursive factorial won't overflow in Racket.