They are by witholding citizenship. Just like the Swede employer was found to discriminate in that case by withholding a fair interview. You are forcing them to greet you in a certain manner or you withhold something of value.
The couple were given a fair interview, and the handshake was merely a single factor amongst others in determining the outcome of that interview.
Not shaking hands isnt sexist. If they refused to answer questions of the opposite sex then say that like you said they refused the handshake. They didn't though, and instead say they had "trouble" or "difficulties" with the opposite sex but didnt describe those difficulties.
Refusing to shake hands is not sexist but refusing to shake hands only from people of the opposite sex is. Stop making it purely about "not shaking hands" because it isn't and, frankly, I cannot believe that you're actually this ignorant about what we're talking about.
Also, since you keep ignoring these questions I'll ask them again:
If I refused to shake hands with any PoC yet felt fine shaking hands with white people am I racist or am I not?
If I refused to shake hands with any member of the LGBT community yet felt fine shaking hands with straight people am I homophobic or am I not?
Also, the Swiss government doesn't need to describe those difficulties because it's blindingly obvious what "struggled to answer questions from the opposite sex," meant. In an interview which, among other things, determines how fit you are to associate with the egalitarian values of Switzerland then showing that you will struggle to speak with 50% of that country's population based entirely on their gender is a big red flag. You can shout "FAKE NEWS" as much as you want but no amount of details will change the fact that they "struggled to answer questions from the opposite sex," to such an extent that the Swiss government, who has let in hundreds of thousands of foreign Muslims before, denied their citizenship because of it.
I understand that you may not care about getting to the bottom of a minorities couple's fate but if im Swiss I certainly don't hold government above scrutiny and would like clearer answers then they've given.
What is that meant to imply? If it's implying what you seem to be implying then I'd rather not argue any further since you're clearly not talking in good faith.