Impressive visualisation. Seems to be an extrusion of the Kadaster (government) building data towards the maximum height of the structure.

Much more precise data is also also available: there are height maps of NL with a resolution of 5 points per square meter, IIRC (not my field). Eg [1], but perhaps more parties do similar work.

[1]: https://ahn.arcgisonline.nl/Postcodetool/s2.html?app=Postcod...

And as mentioned elsewhere, they indeed misrepresent renovations & construction work as building dates.