(Thanks for waiting for the reply.)

I don't think the "open space"/"kick a ball" rules-of-thumbs match with the description on that page. In particular, the area you note I think fits into "managed greenery, located within settlements and nearly always open to general public". You're right that not much of the greenery is grass specifically.

Oops, just a typo. Thanks for spotting it! changeset/60742731

Oh, awesome, didn't realise they existed!

I suspect it may've been accidental; duplicating the tags on the real cycleway on the other side of the oval.

I don't remember; I guess it may've changed in the three years since I mapped this.