First, I don't think it's only possible for skaters to land quads if they are doping. Rika did it. Tuk did it. Other young Russian skaters are landing them. A few young Japanese and American skaters are landing them. I also don't think you can blame Rika's injury on quads. She went to Worlds / WTT with a hurt leg which led her to jump in
way that hurt her back. I'm a huge Rika fan but that was the fault of her own choices and her team's choices.
However, I think the real advantage this drug provides is consistency which is what has really separated TT from the other skaters. When you can practice more, you can become more consistent. That's the primary thing that as separated TT from competitors. And, yes, despite the few regular posters here who will gaslight every situation involving this team, it's pretty obvious clear that if this drug was given to Valieva ( the most naturally talented of the group) it would also be given to it's other members. The doctor probably just miscalculated the dosage for Valieva and it hadn't cleared her system yet. This may not have mattered if RUSADA had still been able to test its own samples, but they couldn't and so the result couldn't be covered up. ( RUSADA fired it's previous head who was trying to clean things up, it's clear they don't want to change)