`iSpecialize` fails on `bi_forall` without eta expansion

From iris Require Import proofmode.tactics.

(* works --- with eta expansion *)
Lemma foo {PROP : bi} {A} (P : A → PROP) x :
  bi_forall (λ x, P x) ⊢ P x.
Proof.
  iIntros "H". iSpecialize ("H" $! x).
  done.
Qed.

(* fails -- without eta expansion *)
Lemma bar {PROP : bi} {A} (P : A → PROP) x :
  bi_forall P ⊢ P x.
Proof.
  iIntros "H". iSpecialize ("H" $! x).
  (* Tactic failure: iSpecialize: cannot instantiate (∀ y, P y)%I with x. *)