If you go somewhere else on the planet, e.g. along the Amazon river, you see that the vegetation data reappears, only to start fading again at zoom level 11 or so. It's too irregular and following satellite imagery too closely to have been drawn from human sources such as parcel data. It must have been built from imagery.

So it looks like it's a deliberate choice on Google's part to only use human-derived features such as a park's outline at most zoom levels, on most of the inhabited surface of the planet.

Google's map shows a relatively tiny bit of land that it labels as the regional park.

Apple Maps, meanwhile, highlights a much larger area that it gives the same label.

Based on the fact that Apple Maps is explicitly highlighting this area, I'm going to guess that it's correct and that entire highlighted area is, in fact, the regional park. So if you wanted to visit Garland Ranch Regional Park, wouldn't you prefer it to be accurately mapped, instead of represented as a tiny slice of green?

Or if you meant that tiny bit of green in Caramel Valley, Apple Maps has it too, it just has a lot more green too that might be interesting if your goal is to visit bits of greenery stuck in the middle of towns.