Trigger collision bubbling to parent through collision layers (2D)

I’m unsure if this is known and I’m just tackling it for the first time but if nothing else I’d like to understand more about the following issue:

I have a parent gameobject with a Cables script that handles collision with cables. That gameobject is in the Cables physics layer, which is set up to only collide with the CablesPickup layer.

That gameobject has a child gameobject called Battery script. The child is in the Battery layer which is set up to only collide with the BatteryPickup layer.

All colliders are triggers. The parent has a rigidbody2D and the child does not.

When the child collision happens, the parent also gets a collision notice. This makes sense if they were in the same layer, but they are not, and that fact seems to be ignored.

This doesn’t happen (the way I ‘solved’ my issue) if the child also gets a rigidbody2D.

I’m wondering if this bubbling is meant to happen even through layers, and if so what’s the reason for it.

I think it is intended.
I have not tested, but maybe you can do a check to see what collider of yours was colliding and run code accordingly with the ContactPoint.thisCollider