Really not true, unfortunately I have more hard drug experience than I should. I've seen plaster sold as crack, as well as chunks of soap. Straight baking soda sold as powder coke, and the person still injected it hoping there were traces of real coke in it.
Heroin (my poison) is worse because of it's unique coloration, it can be mocha brown powder to very very light tan so there are more opportunities to fake out. Tiny amounts of heroin mixed with crushed up xanax, brown sugar, coffee creamer. The worst (or best depends on how you look at it) is getting "dope" that is Fentanyl. I OD'd because of a Fentanyl bag and I was really experienced.
Bottom line you are taking a risk with hard drugs, going IV, it comes with the territory. I mean you buy a bag of powder from a gang member poor it in water and shoot it in your arm, assuming it is what he said it was... not my brightest moments. Thats why you find Your Man and if his bags are good and he's legit to cling to him like the fuckin plague.
Edit: At this point is is largely accepted that Ecstasy pills are going to contain more Meth than MDMA. Good pills just depend on what the ratio is. Pure MDMA is still available in the form of straight crystals called Molly.