Gas peaker plants are needed for nuclear just as much. Generally the article is looking at the most favourable conditions for the technology, e.g. only considering OCC and not interest cost for building and decommissioning of nuclear plants.
Many US nuclear plants are incapable of cycling power output up or down without changes to procedures or equipment.
If you compare France and Germany gas portion of the overall electricity production is quite similar (it's a bit tricky to compare, Germany produced 12% and France 7% but in different years, France gas accounts to 10% of their installed capacity)