Maybe your burner was too weak to burn things lol. When oil is really hot, it burns anything very, very quickly. For most food, flipping while deep frying them does very little because the item is submerged in oil. It just so happened that donuts float, so flipping actually mattered in this episode.

Wiener schnitzels are very thin and pan fried, not deep fried, so it's a completely different cooking process. It's very hard to under cook the interior of a butterflied and pounded slice of lean meat.