Don't all younger Americans do this? Cutting food and pushing it onto the fork requires less dexterity than conveying it to one's mouth. I know Boomers who put down their knives after each cut (never using them to push) and swap their fork around before using it tines-down, and I think it's more comically affected than the tea–pinky thing.
You're not supposed to use the fork like a shovel, is the thing. The tines are to skewer the food, which is why tines-down makes sense. Otherwise, why not a spoon?
Also, the at-distance interaction between two tools requires much more dexterity than making your hand meet your mouth. The latter you should be able to do with your eyes closed.