This wasn't overlooked.
In that same stream the Nechrochasm, which is fully upgraded out of the box, did not have Y2 attack values. The fact is, if all Y1 exotics were going to have the ability to hit Y2 attack/defense values, Bungie would have clearly said so. Their intentional vagueness is all the evidence you need.
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good point. but when the necrochasm was shown it was at 172. what ur saying is that y1 attack cap is 172 which seems sorta sketchy for it to only go up 12 points