We do have a small opportunity to improve, but probably not that significant. Noneless, I think overall it would make things simpler to make the modest refactoring effort.

The last option of merging  `RegisteredServiceDefaultAttributeFilter` and `RegisteredServiceAttributeFilter` is more complicated than all. I am more and more inclined to move everything into the static class `RegisteredServiceDefaultAttributeFilter` and perhaps even rename it, so it's not mistaken for an attribute filter, because it's not.

Attribute filters are intended to filter attributes based on their values. The default works by attribute names. That's the fundamental difference. `RegisteredServiceDefaultAttributeFilter` is also not intended to be overriden or subclasses at all. We'd want to lock it down. So the static option makes sense to me from that aspect.