More Speaking in Ciphers and other Enigmatic Tongues with a focus on SCHANNEL hardening.

Karl-WE 

The link you gave about Setting TLS version you are specifically telling .NET to use a certain protocol.  So yeah, that would work even with the older .NET versions.  the discussion about .NET was the default values used by .NET in older versions and the behavior change for .NET starting in 4.7.  If it is failing it is more than likely that either PowerShell or the Module was coded/compiled for earlier versions of .NET (before 4.7).

Keep in mind that SChannel is an SSPI not the Http protocol. HTTP protocol is WinINET and WinHTTP (HTTP.SYS).  

it breaks down like this:  App ---> .Net ---> WinHTTP or WinINET ----> SChannel

if the app hard codes to use TLS 1.0 it is going to tell everyone else down the line that it wants TLS 1.0.   So by the time it hits SChannel it is just looking to see if TLS 1.0 is enabled or not, and based on that SChannel is going to start doing the TLS Handshake stuff.

In DS we have had to learn all about these other groups things because the cases all seem to just come to us, and we get to deal with understanding WinHTTP and WinINET registry settings for enabling / disabling certain protocols.  This is why we always tell customers to just set DefaultSecureProtocols (WinHTTP) or SecureProtocols (WinINET) to 0xAA0 for the best compatibility and just let SChannel decide if TLS 1.0 or 1.1 should be denied.

Also just think, we don't know what your app was written for.  Was it written to use WinHTTP or WinINET, so we typically have to figure that out as well.