Debris is more generic, that is all
We THINK tunguska was a cometary fragment.
The evidence all points towards that idea.
It was clearly an aerial explosion at altitude, it was celarly too fast for some sort of methane explosion.
I like the "debris" term because it simply emphasizes the fact that bits of stuff are moving through the space around us and a certain amount of it hits us, like bugs on a windshield.
Ed