I rarely comment on source reliability but maybe you're being a little harsh to those who have. So, some Mex places sell good stuff. I'm sure some don't. It's still a dirty country with an inadaquate sewage system so when dealing with a black market source there's a greater risk of contamination.
I never thought vet gear was underdosed. At least there's accountability with the vet houses, as opposed to a UG lab. But I never liked using it because you never know what's added to it that might be fine for a horse but not suitable for a human. (Makes you wonder why so many people experience, anxiety, night sweats, etc on E Q.)