:hook does not defer if on expansion it contains a lambda?

[doolio]

The following use-package declaration does not get deferred as I would expect using the :hook keyword but perhaps this is a misunderstanding on my part.

(use-package yaml-mode
  :ensure t
  :hook (yaml-mode . (lambda () (run-hooks 'prog-mode-hook))))

If instead I explicitly include the :defer keyword as follows it does get deferred as desired.

(use-package yaml-mode
  :ensure t
  :hook (yaml-mode . (lambda () (run-hooks 'prog-mode-hook)))
  :defer t)

In the first case I believe it does not get deferred because of the use of the lambda. The use-package-deferring-keywords docstring states "... :hook ... only imply deferred loading if they reference actual function symbols that can be autoloaded from the module." Is that the case here? Thanks for your time.

[tshu-w]

same issue here.

[skangas]

I can reproduce this on the latest version of use-package. It seems like a bug to me.