I agree about TL0 users not needing to see “My messages” on the sidebar.
I think back in 2022 @festinger was reporting on a behavior I don’t see on meta today, which is that members TL1 and up were also not seeing “My messages” on the sidebar. I don’t know how to replicate that if there are cases where that is still possible on Discourse sites.
I do think that messages should be discoverable still by TL0 users - some sites may have stricter requirements for promotion to TL1. I think just still showing the messages tab on the user menu would be worth considering.