Sorry, but this (& arguments generally relying on photos th show things 'can't be seen') completely ignores the structure of the eye, where the fovea (the part you 'look' with) "comprises less than 1% of retinal size but (is more densely packed with receptors so that it) takes up over 50% of the visual cortex in the brain" so if you enlarged the central 1% of that picture to where it took up 50% of the picture (& shrank the rest accordingly), then we'd be able to tell whether or not something was visible at that altitude (visible, not necessarily 'findable')
I know it's your job & all, but while I don't fly that often (maybe once a month 737 or airbus @ 10km or 11km & once every couple of months in a cessna & 6km ) when I do I make a point of looking (because of threads like this ) & I can't see how people get to a position that it isn't easier to see things in real life than in DCS (or LO etc).
Real life is wide angle with a built in zoom in the middle. SIMs are one thing or the other...