Why do watch faces downloaded from Chrome show "Watch Face Unavailable" in the app?

I notice that if I download watch faces (.watchface files) from a website in the Chrome browser of my iPhone, opening the watch face in the Watch app gives me "Watch Face Unavailable" and below that, "This watch face is not available with your current version of watchOS". However, this message is not correct, because if I download the exact same watch face from the exact same webpage but in Safari, it works fine; Safari prompts to open the .watchface in the Watch app (whereas in Chrome, you have to tap "Open in..." and then select Watch).

I am looking for some confirmation from Apple that Chrome is not supported for downloading watch faces, and that this is intentional.