Did you see the recipe? It’s mixed in together with the egg before you cook it.

Your mileage may vary i suppose. Soy doesn’t seem to be a problem for Japanese cuisine, which I usually consider as tasting very light in comparison to a lot of food.

Tamagoyaki egg rolls for example use soy sauce and are delicious and not overpowering at all.

https://www.justonecookbook.com/tamagoyaki-japanese-rolled-omelette/

100%! Why have just salt when you can have salt and umami!

I also put a little soy sauce in the beaten egg mixture for omelette or scrambled eggs :)