That may be true for the MyPhonak app. I have been an iPhone/watch user for the last year thanks to hearing aids. Prior to that I was an Android user/tester/helper on some android fanzine sites, rooting and modding mostly Nexus and Pixel phones, LG Sport and Huawei watches.
I sideloaded many apps on both those watches with about 95% successful results. The
WearOS will scale most apps to work surprisingly well. Even very large buttons that barely overlap from the side will / or did work fine.
If you are a visual perfectionist then you might not be happy, if function is priority, then give it a try. ADB uninstall will work if the normal OS uninstall does not.