Scanner methodology is not the point as you obviously understand; scanner capability is taking a hit that doesn't make sense.
Since you want to go down that road, though, I find the fact that radio telescopy, which is used in the current day to examine objects hundreds of light years away, cannot tell me what is in the same star system 1,300 years from now to be... unlikely.
Because the concept that existing technology continues to improve is nonsense...
We have terabyte or better super luminal communication, also known as telepresence, and yet, somehow, 1,300 years of technological development cannot reduce a radio telescope into part of a sensor suite that can scan a star system.
Oh, wait, sensors are just handwavium because mechanics in a game that claims to be founded in scientific principles wouldn't do that.
Umm...
Oh, Murdock, you either need to be less intelligent or more, this middel ground thing just makes for easy targets. Radio telescopy was mentioned specifically because of things that EMIT in radio frequencies, you know, the stars I mentioned in the sentance. The objects you are referring to, asteroids and such, are not radio emitters.
If you just want to say that it is Science Fantasy, have the courage of your convictions and do so. For me, I remain convinced that Frontier is just adding slog to the game for no result.
It is fantasy.
You've contradicted yourself by the way.