See attached image. This site is running Slatwall 5.1.021
I would view this as a workaround to possibly allow you to get Slatwall V5 working on a Windows server with IIS. This setting should not be used in a live environment.
What I think is happening is some of the XHR API calls that are part of the newer Angular admin are failing with an error. On Windows IIS server the response is something that Slatwall is not able to process and aborts.
I do not see the same issue on a Linux NGINX setup.
I have not currently have a local Windows IIS environment to investigate further.