Would I have to pay Royalty on video rendered out in Unreal Engine 4, used in a separate game engine?

I am also curious on the answer to this, it’s hard for me to understand why you’d have to pay the same royalty as if you developed your full game in Unreal Engine 4 if you export a video rendered in Unreal Engine 4 - that uses assets generated outside the engine and the engine doesn’t get used past the point of a renderer. Does this mean that you could look at it as “Use us as your renderer but WHAT you do with that content, we’ll decide if we want money from you”? The point where something becomes a product outside of Unreal Engine but remains an Unreal Engine product confuses me. Wouldn’t this mean that monetisation on YouTube with that “Choose your own Adventure” video style people sometimes do means you owe Royalty? If not, why would they be royalty free but doing on a different platform incur a royalty payment?