I own a japanese Pixel 6a and can say that disabling the camera shutter sound works flawlessly with gcam on GOS. This may or may not be a locale thing (?) but that's just speculation from my side, I do not have my pixel set to japanese and I also did not use a japanese google account to get gcam from the play store.
I also still have the sound enabled as having it disabled in Japan is kind of... sus...?