There are three possible explanations I see:
1. Either Starlink is overeoptimistic at its reliability at locating satellites and maintaining separation down to couple of meters of resoultion.
2. or the other operators don't have similar capability and are alarming they can't keep up with moving their satellites that were not designed for so many maneuvers to keep separation.
3. They just want to bad PR for Starlink because they are not happy with aggressive competition.
It seems to me that Starlink is quite precise (or optimistic, I can't tell) at locating their satellites which makes sense. When you have so many you can't be constantly moving them about to keep at least 1km separation. It would probably be cheaper if you could predict the minimum separation to much lower distances, like 50m.
But the other operators either did not anticipate this or don't want to keep investing just to keep being able maintaining their fleet.