What I hear is that the guys at the yodeling festival liked the performance just fine and the only question around was "who the heck organized that superb surprise?"
The village the festival was is a very short distance from Langenbruck and the people there waiting for the pass actually saw them form up and expected them to come back. It was a festivity to honour a famous Swiss army pilot by the name of Oskar Bider who is from and buried in Langenbruck.
The F5's don't have GPS but they do have IRS.
As this was not a full performance but just a fly by, there was considerably less preparation than in a normal display.