Reread Herodotus' report: he claims that the Scythians burned the seeds (τὸ σπέρμα) of the cannabis plant. The seeds contain no THC.

Maybe they were burning buds with lots of seeds

This is second hand at best for Herodotus, so “seeds” could have been an assumption, and it might have just been sort of flowering material including some seeds and resin etc. I think given the described reaction and, you know, thousands of years of history of people getting high from cannabis it is reasonable to assume they didn’t use seeds and only seeds.

I find it really unlikely they were burning the seeds and hot boxing with them, given that burning hemp seeds make unbelievably unpleasant, astringent smoke - about as medicinal as having a tyre fire in your living room.