I am on a pixel 7 pro and have Google Messages installed on a separate profile. I can confirm what malik said ties to the fix.
Disable the default messaging app and the duplications stop. It makes sense thinking about it as I just changed the default. If the default (or what I call admin) profile uses the messaging app it would keep both active in a new profile as the profile wouldn't be admin.
Disable the default messaging app is the fix. It doesn't impact the admin profile.