Those are the facts. Don’t believe this propaganda.
I mean sure, you're right, the weather in the Netherlands is as nice as those picture only for a couple of months per year, but that's not the point of the article, nor does it prove/disprove anything.
The Dutch cycle year round, and while it is true that traffic in the summer is like double, cycling is still the main form of transportation for a significant portion of the population.
I cycle to work most days in Munich, so the climate is roughly the same, and I have rain gear and I'm used to cycling in the rain... I couldn't imagine cycling with an umbrella, but that's a different story... Maybe I was just getting a cold, but I was freezing while being soaked just walking around in the city (with my rain jacket, didn't bring the rain pants).
It is very possible to bike year round.
Anyway, firstly I've been cycling the half hour distance to work for about 20 years now and the number of times it rained is just a small percentage. Secondly, you if possible you can time your usage of the bike according to the weather forecast. Thirdly, we (the Dutch) always complain about everything. The weather included. Still I wouldn't want to live anywhere else (for a long time).