It sounded equivalent to 3-4 grams of dried mushrooms, which is a moderately large dose (well that's what they described as a "sweet spot"), but not out of the ordinary. Trips are graded up to level 5 with is > 5g dried. Terrance McKenna talks a lot about 5g in silent darkness.
I doubt that they're "using very large doses in therapy". Compared to serious recreational users, that is. And in my experience, few if any "unpleasant things" occur with Psilocybe. What things were you thinking of?
They’re using very large doses in therapy, and there are a lot of unpleasant things that are going to happen already even at the minimum effective dose.