Hi, I agree that scrub is a better fit for the old rec ground. However still think that this area should be tagged as brownfield in someway as unlikely to be developed anytime soon due to landfill contamination.

To do this I've added a containing brownfield area (https://www.openstreetmap.org/relation/18517949) - I think this better groups both the containing features.

Hope that works for you too. :)
Thanks