Thanks for the explanation. I don't remember any "speelbos" signs; generally it's "Gelieve steeds op de paden te blijven" nature reserve area. Maybe outside the blooming season it's less strict? 

I wasn't able to find any information online: it's not on the map at https://www.visitvlaamsbrabant.be/wandelen/vind-een-wandeling/reebokwandeling and it's not listed on the municipal website: https://www.visithalle.be/nl/speelbos-zavelput