Speaking from my experiences, I believe the signs suggest that the powders have been cut.
Example 1:
All UGL Test Prop 100mg/ml I have used (Geneza, "Nordic UK" 's Virormone) were noticeably stronger than my homebrew Test Prop 100mg/ml. My strength gain was much bigger with UGL Test Prop.
Example 2:
My Tren brewed from Fina pellets (legit vet product) were WAY stronger than my homebrew Tren from chinese ingredients.
My weight gain from about 100mg from Fina pellets were the same as my weight gain from about 200mg chinese Tren (100mg Tren A + 100mg E). In addition, the side effect (insomnia) was way stronger with Fina pellets.
Example 3:
One time, I noticed my new viagra, Tren A / E, and Sustanon had a similar fragrance. I know from experience as well as from common sense that they should not have a similar smell, so I asked the source why they all had a similar fragrance. He did not have a direct answer other than "purity 98%."
I used the products, and from the results and side effects, I knew they were real stuffs, but for sure, they had been cut with a compound that emitted the same fragrance.