I've cycled in most of those cities, and the list is bunk.
Right from the start, Amsterdam comes in first. Not a terrible city for cycling. Beautiful too. But it might be one of the least bikeable cities in NL. Throngs of tourists, narrow streets and probably the highest percentage of foreign-trained drivers. But it is the most famous, and has built terrific structures for bikes, so there we go.

I suppose that the list is not so much about actual bikeability, but an account of who's been making progress. All in all a good thing. These twenty cities serve as good models for others.