Over the last four years the USD has moved in the range 0.92-1.03 CHF (a +/- 5.6% interval around the midpoint). The average rate is 0.985, the standard deviation 0.019 (2.0%).

Over the last four years the EUR has moved in the range 1.06-1.20 CHF (a +/- 6.0% interval around the midpoint). The average rate is 1.117, the standard deviation 0.034 (3.1%).

Even though the exchange with the USD is slightly more stable in this case (it depends on the period and metric chosen) saying that it's pegged is an exaggeration.

By the way, the CHF was not pegged to the EUR either. There was a minimum rate set by the SNB at 1.20 but it floated as high as 1.26 in 2013.