TLS 1.2 and wpf apps

I have a wpf application, windows service and a console application in framework 4.6. These 3 applications uses a common wcf service to which TLS 1.2 is enabled. TLS 1.0 and TLS1.1 are disabled. I have added a appcontextswitch to false in app.config of all the three applications. It worked in windows 10 machines. But this switch didn't work in windows 7/windows server 2008 machines. But when I changed the switch to System.servicemodel.dontenabledefaulttlsversions it worked in both windows 7, 2008 server and windows 10 machines. Is this ok? I am confused with the switch DontEnableDefaultTlsVersions under different and system. Servicemodel.can anybody help?