"an attacker would have to send a specially crafted HTTP request to the affected system"
"Disable IIS kernel caching"
That's definitely not client-side at all. IIS is the thing that uses http.sys, and classic ASP.NET apps (not the new Core stuff) are usually deployed with IIS.
Historically, the schannel infrastructure has been secure, especially as compared to openssl.
>How is a goddamn HTTP parser in THE KERNEL more secure than a crypto/TLS library?
Because, lets face it, openssl is a shit project of legacy code no one wants to fix and https a design by committee standard no one can work well?