I get exactly the same in Emacs 28.1.

I never use diary, so I don't know whether this is what's expected or
not.  Could you explain what you expected to see here, or whether you're
seeing something else in Emacs 28.1?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no