My theory is that both the tie rods and cups wear as might be expected but the issue only arises when we diligently look to refurbish them.
There's no way to reassemble the 'worn' parts back into their original comfortable orientations with respect to each other and upon reassembly, they seem notchy.
One day, I'll try some valve grinding paste on an old tie rod set to see it it brings them back to 'reasonable'.