As mentioned here already, the paid relays main use case is that you view global feed only from them, and thus getting less spam. But it is also a good way to keep relay operators monteized - which is important to allow scaling.

I suppose now as you have higher ping to the .eden and other USA-based relays, so you get most of the posts already from other relays. It just might be that these are the not even queried from the payrelays? This is just my guess - I have not checked how it is actually implemented.

Amethyst has quite good filtering in global even for public relays. I paid for few too but have stuck to "full" global .