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Although it's easy to "create" pseudo-science with EEG data, the presence of EEG by itself does not mean straight pseudo-science. It can be used correctly, and it's actively used in the medical field to detect brain diseases, for example.
*That said, I'm not saying the study here is to be believed, I have not read it, just commenting on EEG
Like you mentioned, Ancient Egypt did have slavery, so even if there's evidence of temporary villages for paid workers, it's very hard to believe slaves were also not involved as well on projects of this scale.
Even on the hardly off chance that there were 0 slaves near the pyramid, the whole material gathering and transport job to the pyramid site was an insanely huge amount of labour as well.