This is true but mostly irrelevant, because mapping data is the least valuable self-driving data. Google focuses on it because Google has it already. Google Maps is one of the things Google has that few else have, so it's obvious for them to build their technology on it... nobody else can copy them.
But if you have the most cars collecting the freshest data, you still have to bear in mind, the car collecting that data, is currently relying on the old data. Which means your cars can't trust the map data. And the reality is, with how much things in the real world change, your map data will never be trustworthy. You can have it, but you can't rely on it.
Which is a better self-driving car? The car that can look at a cloud-based 3D map of every object in the entire town, assuming it's current, and decide on a route? Or the car that can ping Google Maps, get told "turn left on Main, right on Washington" then entirely from it's live surroundings, decide how to drive?
