Not true. SpaceX envisions using Starship (the same vehicle SpaceX would need to be able to launch 12,000 satellites) for satellite interception and capture. No Starship, no 12,000 satellites.
You don't need Starship for limited constellations to cause issues with Earth based observations though. Also SpaceX isn't the only one that's going to be wanting to make a constellation.
Well in that case, we've had limited constellations that cause issues for Earth based observations for decades. (Note: this is one hint that the risk here is exaggerated... dealing with satellites has been a thing for a very, very long time. Filtering out satellite tracks is easy and common, and modern digital imaging and data storage techniques have made satellite track removal ever easier. And many satellites--particularly space stations--are orders of magnitude brighter than Starlink satellites will be.)