Maybe. Rust as a core language is less productive than ocaml, by a lot. But Rusts standard library is just so much better than Ocamls (including Jane Streets version) - which tends to even it out.
I think there’s probably a hidden coefficient here: I would readily believe that an experienced OCaml developer is more productive than an equivalently experienced Rust developer, but that a junior Rust developer is probably several times more productive than a similarly junior OCaml programmer.
(This is not unique to this pairing of languages.)
(This is not unique to this pairing of languages.)