I don't think this is comparable. One is generally taking long-time exposures for astronomy pictures (hence the streaks).

So if the satellite is simply blocking light, in the worst case, it will block the light of a star, maybe for a few milliseconds(?) dimming the star in the final picture by a minuscule amount.

This might still be problematic (influencing spectroscopy? dimming the star slightly, influencing some measurements there?) but probably still better than potentially mixing in light from a difference source (?)

astronomy today point to a small piece in the sky to measure some binary star that is barely one pixel on the sensor. now you covered it with a black satellite right when then unique event was about to happen... did it not happen or was hidden by a new satellite?

also, black coating is old news. very old news. and musk said he didn't consider for starlink because he doesn't have to pay for something that doesn't make money directly for himself. so this whole discussion is pointless.