To my knowledge Shcherbakova wasn't injured last year, it was that she got sick with pneumonia, she took off most of November and decided to return early to compete at Nationals which probably led to her basically limping through the rest of the season - at Worlds or WTT it was mentioned that she was still training with restrictions from illness. Kostornaia and Trusova were injured at various points through the year, but they both seemed to have healed at this point and the injuries don't appear to be multiple seasons of injuries like with Rika.
Per your own comment (in response to my question) Rika's been struggling with injuries the last 2 years and here she is in the offseason leading up to the most important season and limping through exhibition skates...I get that injuries happen and I get that exhibitions are likely a source of income for her, but knowing that's she's struggled with injuries for the last few seasons and seems to either have been reinjured or is still injured from what happened at Worlds. It makes me wonder, should they be approaching her healing process differently seeing as how she can't seem to get healthy or stay healthy? If she's going to have a fighting chance at the Olympics she's going to need to be in optimal condition and it seems like maybe the continued pushing through with only modifying her training isn't getting her completely healed or maybe in modifying she's putting stress somewhere else trying to compensate for an injury (I've been there, done that)