Went to check again yesterday, this time I attempted to walk through the forest to any possible connecting street. I've taken some pictures (https://queerthoughts.org/media/osm-notes/3546618_1.jpg, https://queerthoughts.org/media/osm-notes/3546618_2.jpg, https://queerthoughts.org/media/osm-notes/3546618_3.jpg, https://queerthoughts.org/media/osm-notes/3546618_4.jpg) and updated the situation in https://www.openstreetmap.org/changeset/147150170.

So to conclude, there's no connection with Terstrekkes, the existing path connects to a private garden which has been fenced off (see third picture). It's possible to walk to Kasteelstraat, but vegetation is very dense (see fourth picture).

Another detail: I've used obstacle=vegetation instead of overgrown=heavy. The former is documented on the wiki and sees ~500 times more use according to Taginfo.