Is the following code intended or just due to carelessness?

[qwfy]

In the file os_db.ml, there is this chunk of code:

let transaction_block db f =
  Lwt_PGOCaml.begin_work db >>= fun _ ->
  try_lwt
    lwt r = f () in    (*****A*****)
    lwt () = Lwt_PGOCaml.commit db in
    Lwt.return r
  with e ->
    lwt () = Lwt_PGOCaml.rollback db in
    Lwt.fail e

let full_transaction_block f = (*****B*****)
  Lwt_pool.use !pool (fun db -> transaction_block db (fun () -> f db))  (*****C*****)

I'm little confused, why the f at B gets wrapped to a fun () -> f db at C and passed to A?, couldn’t we just pass f at C and replace A with let r = f db?

If it's just careless writing, I think it should be corrected, it confuses beginners such as me and prevents refactoring (you know, those cases you think a chunk of code is useless, but you don't have the gut to remove them).