Fine, but you never answered whether that understanding is in the tantras themselves, in self-commentaries presumably written around the same time or not long after, or in significantly later commentaries. Later commentators would have a strong vested interest in tying up any apparent loose ends or ambiguities, and they would do so according to their scholastic monastic training.
That is true. I have to wonder whether the early Dzogchenpas ever got in trouble and were punished, though. That would account somewhat for the emphasis on secrecy. Some of the early stories about Vairotsana involve persecution, right? Certainly, tantrikas in general stirred up controversy with their conduct. I guess some tantrikas would've been surprised and taken aback by Dzogchen.and this information was voluntarily provided under no threat of beheading.
I would agree, of course, that medieval India was a more hospitable climate for differences in spiritual doctrine and practice than was Europe at the same time. Tibet usually was, too, though I think there were some unfortunate sectarian conflicts.