Parallel kerbs can be quite dangerous for cyclists. A slight lapse of concentration and you can be off your bike, and possibly injured badly enough to end up in hospital.
Like so many things, this doesn't have to be the case.
The kerb shown here is one of many "forgiving" 45 degree kerbs in use in Assen. These kerbs make it possible to cross from the cycle path to the pedestrian path without falling from your bike. They reduce the risk of injury due to a lapse of concentration.
The video demonstrates how you can ride up and down the kerb without losing control of your bike.
This kind of innovation makes the cycling environment very forgiving of errors, and keeps down the injury rate of cycling. It is one of the many very small details of the Dutch cycling environment which add up to it being very safe overall - the concept of making the road environment more forgiving of error is called sustainable safety.
"Parallel" refers to the kerbs being parallel with the direction of travel. Even a very small gap can cause cyclists problems if it is parallel.