I did offer William's Rethinking Gnosticism. Another is Karen King's What is Gnosticism? (which has an entire subchapter addressing Jonas).

And I wasn't directing any of my comments at OP's question (largely because the later beliefs around the demiurge were a confused mishmash of trying to make sense of earlier ideas in a new philosophical context). I was cautioning anyone who read your comment and specifically the book recommendation that it reflects an out of date and inaccurate perspective.

As for his accuracy in the actual beliefs of the people in question, I'll leave you with a passage from Karen King's aforementioned work on the topic:

The second dominant approach, typology, uses phenomenological method based on inductive reasoning from a literary analysis of the primary materials. Gnosticism is defined by listing the essential characteristics common to all the phenomena classified as Gnostic. The most accomplished practitioner of this method was Hans Jonas. His greatest contribution was to shift the discussion of Gnosticism away from genealogy to typology. Rather than define Gnosticism by locating precisely where and how heretics deviated from true original Christianity, Jonas defined the essence of Gnosticism by listing a discrete set of defining characteristics.

Unfortunately, detailed study of the texts has led scholars to question every element ofthe standard typologies constructed by Jonas and others. In particular, specialists have challenged the cliché of Gnosticism as a radically dualistic, anticosmic tradition capable of producing only two ex­treme ethical possibilities: either an ascetic avoidance of any fleshly and worldly contamination (often caricatured as hatred of the body and the world) or a depraved libertinism that mocks any standards of moral behavior. In fact, the texts show a variety of cosmological positions, not only the presence of anticosmic dualism, but also milder forms of dualism, transcendentalism, and, most surprisingly, both radical and moderate forms of monism. The majority of the texts show a tendency toward ascetic values much in line with the broad currents of second- to fifth-century piety, and some argue for the validity of marriage, attack the human vices of greed and sexual immorality, and promote virtues such as self-control and justice—also ethical themes common in their day. That no treatises supporting libertinism have been found may of course be simply a matter of chance; it is nonetheless telling.

• What is Gnosticism? p. 12-13

You can't just take the heresiologists at face value, and Jonas was writing at a time where many key texts had no discovered primary sources to contradict what the heresiologists were claiming about them and their traditions. So he erred on the side of taking them at their word. Criticisms about libertinism by ancient Christian authors towards their ideological opponents (present as early as Revelations) were taken for granted and incorporated into the speculation, and yet there's been no evidence of such attitudes in a trove of primary sources discovered since.

It is obsolete and outdated, even if it was among the better texts in its time and place.

Anyways, this conversation is now going in circles. Take from our exchange what you will. I'm glad you enjoy the book, and I'm not trying to take away from your enjoyment of it.

But if you really care about the topic of Gnosticism, I'd suggest looking a bit more into recent work on the topic, and the two books I mentioned would be a good place to start.