I think one factor is that the PS2 generally outputs 480i signals with scanlines shifting vertically every frame to fill gaps (so you don't see them unless you'

I think one factor is that the PS2 generally outputs 480i signals with scanlines shifting vertically every frame to fill gaps (so you don't see them unless you're tracking a vertically moving object), while many CRT shaders default to simulating a progressive signal with fixed scanline gaps.