Seems like the real issue here is that nobody can trust anyone else. What i mean is that we are talking about illegal drugs being illegally manufactured by unlicensed and unregulated people (i will avoid using the word company to describe them) using powders of variable quality. These are then bought illegally over the internet before being illegally shipped to the end user.
From the point of view of the end user, you simply cannot trust any lab test coming from the person making the drugs. From end user point of view there is no way to determine if the maker is 100% genuine and the result is 100% genuine, or the maker is a scammer and the result is somehow not trustable.
From the point of view of the maker, there are a lot of untrustworthy customers. For example my goods never arrived please reship when actually they arrived fine but they want more for free. Or it could be the end user is actually a shill for a rival and even though they haven't actually purchased anything they can spread as many rumours of poor customer service or bunk goods.
Basically everyone is out for themselves. They will either behave honourably and look after themselves by providing excellent service and products (e.g. pharmacist on this very site), or they will screw everyone and anyone over for gain (and as I have said this could be the seller or the buyer).