Sorry for the delay, I’ve been busy. Yes, I think I will explicitly state on my product’s showcase map that the assets are allowed and free to use. And also yes! I received an email to ask any questions, doubts, etc. However, honestly? They are taking a long time to respond. 
But, let’s see what happens. I put in the documentation that the products are free and “all of these assets may be used under the following conditions from Epic Games itself: UE-only content - Licensed for use only with Unreal Engine-based products”