Trailmarkers have been up for discussion for quite some time. The markers you are referring to are not considered trailmarkers by the guidelines as these are directional markers to bike junction points, which is not a set out trail but rather considered infrastructure for biking in the Netherlands.
Examples of trails are ones that highlight the environment, such as for example het Pieterpad: Pieterpad in etappes . A lot of locations also have very specific trails, see also: Appeal for restoration of all the removed trail markers in my area
And also please don’t shoot the messenger.