So how is such a carefully curated prop not an Easter egg?
I suppose that would depend on your definition of 'easter egg.' Here's mine: Something that was meant as a joke and not meant to be taken seriously. Such as seeing R2D2 in the wreckage of the Federation starships over Vulcan in Star Trek '09.
In this instance, there was no joke. Adam Soong pulled that old file out of his desk for a reason. And it was dated 1996 for a reason. Whether that reason is because they're trying to retcon the Eugenics Wars to take place later and Khan was just escaping Earth before they happened, doesn't really matter, because...(see next.)
To reflect real life. So not pointless. Attempting to answer fan complaints both for and against changing "canon".
We somehow how managed not to notice the behind-the-scenes wars up to 1996 (but explained in the first Khan novel) and we are probably heading to more real-life battles now.
Except no matter how hard they try, or how far into the future they retcon the Eugenics Wars, this show is still not reflecting 'real life.' There's no way anyone will be sending a manned mission to Europa in just two years from now. We can barely get another person to our own Moon by the next ten, and even if we did, that person will probably be from the Chinese Space Agency. And we certainly aren't going to have any upcoming wars that have anything to do with genetically-engineered supermen.
So trying to retcon the wars is a pointless endeavor, IMHO. If they'd just made SNW a reboot
like it so clearly is already, then they wouldn't even need to bother retconning anything. But their insistent need to link the show to TOS and try to 'fix' historical inaccuracies from that show, while at the same time making other things different with no explanation at all, makes very little sense to me.