This is not true.*
I have had a full ++++ experience on a single hit of lsd (~150-175ug). As mentioned, saturation of relevant receptor sites occurs around 1.5mg-2mg and after that lsd will start to target the dopamine, histamine, and other receptors responsible for the "negative" physical sensations and thoughts.
In short, more drugs =/= more insight. Less is more friend.
*To be fair I should say this is very, very rarely true.
I simply don't agree with you. Maybe you're lucky as hell but most people can't get ++++ experiences on higher doses of LSD, let alone 150ug. With an increase in dose comes a hugely more intense effects profile and insight for many people.
Plus, come on now, saturation level of 1.5-2mg - ok, what does that prove? certainly NOT that anything beyond your 150ug ++++ is just worsening physical symptoms, because theres a good 1350ug different between the saturation and your dose. that is a lot of room for a lot of shit to happen