Cannot get camera stacking to work in a way that isolates post processing effects to just one layer

I have 2 cameras, Main Camera and Glow Camera.
I want objects on the layer “Projectile Glow” to have bloom applied to them.
I’m using the Universal Render Pipeline.
This is the Main Camera, culling mask is set to everything but the layer I want the other camera to render, and the Glow Camera is added as an overlay.
See screenshot 1.
This is the Glow Camera, culling mask is set only to Projectile Glow, and it has the post-processing volume.
See screenshot 2.

However, no matter what I do - it renders the bloom on everything. I can’t attach more than 2 images, but I have 2 cubes side-by-side, one is on the Default layer, the other is on the Projectile Glow layer. BOTH have the bloom affect applied and I cannot figure out why. I have spent hours researching trying to figure it out, all the tutorials I have found do it pretty much the exact same way from what I can see, yet it just doesn’t work.

Any help would be greatly appreciated, thanks.