Ineffective inhibit-message-regexps

I would like to ignore some messages, and inhibit-message-regexps (new in Emacs 29) looks like just the thing I need.  However, I find it does nothing:

- - - -
#!/usr/bin/emacs -x

(add-to-list 'set-message-functions 'inhibit-message)
(add-to-list 'inhibit-message-regexps "matching")
(message "%s" "this is a message matching one of `inhibit-message-regexps'")
- - - -
$ ./inhibit-messages.el
this is a message matching one of `inhibit-message-regexps'
- - - -

I see the same behaviour if I run this in non-batch, with the message printed to both the echo area and the *Messages* buffer.

I notice inhibit-message-regexps mentioned both on Emacs Stack Overflow (https://emacs.stackexchange.com/questions/52846/how-to-remove-message-indentation-setup-for-shell-type-sh/85114#85114) and Reddit (https://www.reddit.com/r/emacs/comments/1m74q7p/comment/n4r4fck/), so presumably this works for other people.  Can anyone suggest what I’m missing?

-- 
Peter Oliver