:hook forms not equivalent

[just-walk]

When adding julia-snail-mode to the julia-mode hook, different forms of the use-package syntax that should have "equivalent" behavior are in fact different. (https://www.gnu.org/software/emacs/manual/html_mono/use-package.html#Hooks)

This first form does what I would expect it to do.

(use-package julia-snail
  :ensure t
  :custom
  (julia-snail-terminal-type :eat)
  :hook (julia-mode . julia-snail-mode)
)

The variable julia-mode-hook then evaluates to (julia-snail-mode).

This second form shortens the hook declaration. By the documentation, this should append -mode to the package name and add it to the hook specified. In this case julia-snail-mode should be appended to julia-mode-hook.

(use-package julia-snail
  :ensure t
  :custom
  (julia-snail-terminal-type :eat)
  :hook julia-mode
)

Instead, variable julia-mode-hook evaluates to (julia-snail).

What's going on? Is this a bug in use-package, or am I misunderstanding the docs?