Sorry, what? I think Sasha knows better who trained her for this tournament. In a recent interview to the question (What was the most memorable tournament for you?) she answered: "The most memorable tournament was junior worlds 18. It took a long time to prepare, all the coaches, except for Sergei Alexandrovich Rozanov, were at Olympics. We were preparing two quads for the world championship, before worlds we had the Russian Cup final, there I tried two quads for the first time".
I think it is clear that in the 17-18 season the main coaches were busy preparing for the Olympics (in February they were not at all in Khrustalny). Rozanov was with Sasha at all Russian Cup stages and spent the most time with her in training(like with Kamila and Daria this season). Sasha's 4T is largely his merit.
Edit: And of course, I forgot Sasha's words on Instagram about importance of Sergei in her career "Special thanks to Sergey Rozanov for his work and faith in me. He says little about himself, preferring deeds and not big words, but without his painstaking and honest work, there would be no achievements and victories. At the decisive moment, he offered me his shoulder, he is my reliable friend."