Thank you, I never paid attention to it!
I only see this separation in W5100 reference schematic, but probably my circuit diagrams are out of date.
Did you look how they are “separated”? Most probably you see ferrite bead between them, thus from DC perspective it is the same signal, and it has deviations only when there’s a heavy noise at specific frequency. If you design system properly and have clean power supply, then ground filtering has no sense (to addition to analog 3V3A filtering).
