Why is mixing a thing suddenly?
Definitely not new, people have been doing this since at least the 90s, when I was a kid.
I also know plenty of Japanese people who say dipping the rice lightly into soy sauce is the correct method, so take literally any “sushi etiquette” guide with a grain of salt.
Eat your food in whatever way brings you joy. Anyone that says otherwise is a pointlessly-gatekeeping idiot.
Not a chance… he’s never included that much information in so few words.