This is an old article I read long before and magnus, whom I agree with here in his interpretation of Sam, posted it here before too if I remember correctly. Sam is not the type of person who would draw such radical conclusions based on almost nothing. He is very respectful and also conservative. While he hypothesizes sometimes, he never states things as fact without evidence and is always flexible. He states all the facts he deems relevant often contradictory. That's just not his style. People can post on his blog and he answers honestly, so I don't buy any of that interpretation. Also he has read widely, including Samten Karmay and others, who state the texts how Dzogchen was actually banned by local rulers in North India and never was properly established openly before it went North and lots lots more. This is a big field not just summed up in a few pages of an article. Attacking Ekajati's protected lineage merely after mis-reading a short article when someone just finished their PhD is going over the top for probably other personal reasons.
The seventeen tantras cannot be firmly dated earlier than their initial production by Dangma Lhungyal. Between him and Nyanban Tingzin Zangpo there is only a single master, Bey Lodro Wangchug (one Rinchen Bar is also sometimes added to the list). We can positively date the end of Chetsun Senge Wangchug's life to the early 12th century.
Supposedly, Lodro Wangchug concealed the Seventeen Tantras in Samye, and Dangma Lhungyal removed them from hiding at Samye and gave them to Chetsun.
The Vima Nyinthig is the earliest text to list the seventeen tantras and their subject matter. For the most part, the Vima Nyinthig is the terma of Chetsun. Thus, teachings like the Tshig gsum gnad rdeg, etc., also cannot be dated earlier than the late11th --early 12th century.
These are the kinds of facts that limit textual analysis. You can only go by when a text actually appears.
There are three masters between Vimala and Chestun, and since tradition holds that Nyingthig tradition was a single lineage until Chetsun, we would have to accept that these three or four masters passed on several thousand handwritten folios i.e. the several hundred pages of the seventeen tantras as well as their lenghty commentaries, between roughly 800 AD and the early 12th century when Chetsun passed on his lineage to Zhangton Tashi Dorje who lived between 1097 and 1167 around 1123 when they met. Thus, the latest date for the seventeen tantras is 1123. Obviously they were composed earlier, since the Vima Nyinthig is based on them.
Zhangton's son, Nima Bum, wrote the earliest independent commentary on the Vima Nyinthig. It is a very interesting text, and is dense with citations from the seventeen tantras, and is the model upon which Longchenpa based his own Tshig Don Mdzod. Nyibum was also a disciple of Jetsun Dragpa Gyaltsen and was closely connected with the Sakya school. The Nyinthig teachings were a family lineage for three generations i.e. Tashi Dorje, Nyibum and his nephew, Guru Jober.
The commentaries for the seventeen tantras are first mentioned by Longchenpa and so cannot date later than he. It seems unlikely they were actually authored by Vimalamitra, but who knows. They were mostly likely composed in the early 13th century since they must have been known to Kumararaja. Perhaps they were composed by Nyibum, since he was known to be a great scholar, his title was "Zhang mkhas pa" i.e. "Zhang Pandita". Or there were three masters between Nyibum and Kumararaja, Jober, Sangye Gyab and Melong Dorje, all thirteen century masters. Anyone of them too could have composed these commentaries.
Jober, was known to have many disciples. He passed away in 1258.
The Khandro Nyinthig was produced in the mid-to late thirteenth century after Jober started teachings Vima Nyinthig widely. We do not have good dates for Pema Ledretsal, the terton for the Khandro Nyinthig. All we know is that he was active in the mid to later thirteenth century and that he did not life a long life.
The Khandro Nyinthig presents itself as a commentary of one tantra specifically, i.e., the Longsal Tantra. Thus this tantra predates the Khandro Nything but is later than the Seventeen Tantras, it was probably composed in the early 13th century. The Khandro Nyinthig is the earliest text that mentions the Longsal Tantra. This tantra summarizes all the topics of the Vima Nyinthig and the seventeen tantras into 113 chapters, giving detailed instruction for practicing creation stage, completion stage as well as Dzogchen tregchö and thögal. Most later Nyingthig termas atrributed to Padmasambhava cite the Longsal tantra extensively. The Khandro Nyinthig also begins the tradition of six short tagdrol tantras. Notably, it has a concise version of the Single Son of the All the Buddhas, originally found in Ser Yig Can of the Vima Nyinthig.
We can trace the ideas and their spread pretty well after Chetsun. We cannot trace the origin of these texts at all well, and so have to rely on the history of the seventeen tantras and the Vima Nyinthig as presented in the Lo rgyus chen mo since this is our earliest source of information about this tradition. We have to admit that objectively, we really do not know anything about this tradition prior to Senge Wangchuk.