Interesting.  The source you give adds "Baron" to the name (but surprisingly only in French) and not "de Châtelet".

Anyway, I would like to avoid the usual edit war if someone claims to have seen a sign with another name.
It is difficult to see on Mapillary but it looks like the golden sign next to the gate says something like "Parc ××××× Pierre Paulus Park".  (××××× == Baron?)
https://www.mapillary.com/app/?pKey=412258123720945

If a survey find something, we can either choose to use Pierre Paulus for the name and Pierre Paulus de Châtelet for official_name or short_name and name respectively; or with/out "Baron" in the name.

I suggest leaving it open for some time until we can survey or find more pictures.