text: The city can officially call it whatever they want. OSM doesn't necessary go by that alone though. Especially since in a lot of cases cities consider any public green space a park for zoning purposes. Even if they have zero park like features outside of grassland. That's not how we tag things in OSM. Things need to be ground verifiable. I can verify on the ground that this is a sports complex. I can't do the same to verify it's a park. 
  
  In this particular case, I think leisure=sports_centre fits better because 99% of the place is made up of sports pitches. I see no walking trails (aside from to get to the sports pitches), picnic areas (except for the one next to the soccer fields), bbqs, playgrounds, or anything else that would qualify this as a park. Aside from mown grass, but that's not enough on it's own to qualify something as a park. All (or most) sports related infrastructure in America has mown grass, a paths to get to the fields, and places where people can sit to watch a game. 
  
  Also, the place has "Sports Complex" in the name. So clearly the city considers it one. It's always easier and leads to less arguing to tag things based on the name. Along with what's on the ground. If there was playgrounds, BBQ, or other park like features then maybe I'd agree it should be tagged as one, but clearly people are mainly coming here for the sports fields. Not to BBQ while their kids play on the (non-existent) jungle Jim. In the meantime, I know there are statues of giant soccer balls and footballs there. Are those things more conducive of your average local park or a sports complex? 
  
  In the meantime, the benefit to tagging it as a sports center is that people will be able to find when looking for sports centers to play football or soccer at. 