There is no archaeological indication whatsoever if only to the contrary they were "Egyptian" during this time, or ever, let alone even a culturally distinct group prior to sometime between the 11th-15th centuries AD. This is pure gobbledygook.
The connections are documented in my series of books on comparative cosmology. You're right that much of it doesn't come out of archaeological evidence (some specifically does), it comes largely from direct comparisons of a living culture's civic practices, rituals, symbols, myth and language with what has been documented by archaeologists and Egyptologists in Egypt. There aren't a great number of people who are well-versed in the Dogon side of it, but I'd be happy to hear contrary points of view.