It’s not crazy, it’s simply not true. 
There’s some confusion here. You can’t have physics simulation with no collision, for example:
- above, I’ve removed collision from that cube; it will never simulate physics on its own. That’s unless it’s attached to something that does have collision and is simulating, here - the root. That’s referred to as welding in UE4.
Do note that having and using collision are 2 different things!
Simplified is used for physics sim.
In your case you had a root mesh simulating physics and an attached Shield Static Mesh that also simulates. The latter can have collision but should not be simulating physics separately. That’s the job of the root component to account for the welded on component:
In short:
- root static mesh (yellow small box) - has collision and simulates physics
– shield static mesh (big box) - has collision but does not sim physics
The yellow box is using its own & the blue box’s collision when simulating. This way, theoretically, those 2 entities should never interact with one another (unless overlapping ofc) but can interact with the world using their own collisions.