I agree that it isn't valid, and I get that same error when I try to set the timezone to CST after I connect.
The difference though is when the client sets that timezone when connecting, that's when the error is listed as FATAL and the connections fail in 9.6 (and also 9.3 according to the previous thread), where as the connections didn't fail in 9.2 and earlier. That's the behavior change I'm looking to account for.
Don.