The problem is that a lot of other people DO take them seriously.
Yeah I've seen it.
But the thing is... Who's "right" doesn't matter, because LFL has the final say, and if they say a A-Wing is 9.6m and Home One is 1200m, then that's how big they are.
The only way someone could reasonably argue otherwise if they had access to the original model, and could say that model was 100% accurate to scale. Because even with the original model unless you can say for sure it was proper scale you can't really say anything.
I saw a picture from somewhere that showed the cockpit of the Falcon that was so small, chewies feet hung out the bottom of it. Yet it was a functional set used in the movie.
But again, the correct size is whatever LFL says it is. Maybe the A-Wing in RotJ wasn't actually 9.6m but it seems pretty clear the ones in Rebels are.
from Episode IV...