Because of data chaos, my guess, it is only that, is that the reason the historical data all agrees is that the various sources for historical data are copying from each other, which could effectively mean they are all copying from one source. Considering all the trades and different venues that are supposed to be reporting, the late reporting, the errors in reporting, the screw-ups and the corrections, and the large number of trades and their frequency in an active market, it would be a miracle if any of the consolidated data is highly accurate. Best to just consider it all as approximate.