I think the man was making the claim the Gnostic sects predated both Judaism and Christians by quite a bit based on some readings that have survived from the much earlier Hermetic text.
Gnosticism Like Buddhism is not a Religion but a Mental and Spiritual Science....Yoga
Gnosticism is a Knowledge based system of ideas based on personal experience of Spiritual phenomenon....Spiritual Science or Technology and Techniques.
The Term Gnosticism is a Greek Name Given to this body of Knowledge....So Yes the knowledge predates Judaism (but not the name) and Christianity
going all the way back to the Founding of Egypt, Sumer and the Indus valley Civilizations - Thoth/Hermes Trismegistus.
In Hellenistic Egypt it grew and became popular among the general populace as the Greek Mystery System/Schools of Esoteric/Sacred knowledge, where in sense for the first time it became available to the general public....The Leaders or Teachers or Guardians of this then Secret Knowledge became known as Gnostics people or individuals with Gnosis/Knowledge.