Your reference are case reports and even has this disclaimer "While TSW was considered the most likely diagnosis in these children, confirmation was not possible partly due to the fact diagnostic criteria for TSW did not exist when they were first assessed, and partly due to the inability to completely exclude all differential diagnoses".

And of course you can ethically confirm this data through a clinical trial. Enroll kids with specific diagnoses, treat half of them with steroids, half without and compare outcomes.

I'm not saying TSW doesn't exist, but the evidence for it doesn't look very conclusive.