Hi,
Sorry for the delayed response.
I have noticed this issue as well...notification sounds are intermittent for Mail and Messages.
My M1 Mac mini is still running Monterey (due to audio software/hardware incompatibilities). I checked my notification settings for Mail, and there is no longer a Play sound for notifications setting for Mail like there is for Messages.
I don't have a Ventura Mac here currently, so I will test it out and get back to you.
C