The Starlink constellation has already been described as being passively de-conflicted, meaning that, as designed, no Starlink satellite had to maneuver around any other Starlink satellite. The positional accuracy of the Starlink satellites is known by SpaceX to the precision of meters rather than kilometers. I’d need to dig it up the source again but Starlink satellites pass within kilometers of each other daily. Starlink already has over 1000 satellites at several of its altitudes.
While yes it’s true they have to avoid space debris with a wide berth I don’t really include that in the argument as that is a true statement no matter how many or how few satellites are in any given orbit.
It’s more a matter of poor control and poor altitude maintenance of other satellites. That’s a matter of regulation rather than a matter of an actually limited resource. For example Starlink currently uses 10km or 7km gaps between its shells but they vary in altitude significantly less than that and could be closer if allowed to be.