If you install the google apps on an iPhone it gets closer but certainly not out of the box. I don't have stats on maps app usage but apple maps is at least used by some folks rather than google maps which means google is not able to collect valuable location data for some users. And on ios google maps is not able to collect location data when it is not running so the collection of data is much more limited for google.
To your point, however, they still collect quite a bit.
Google Maps isn't able to collect location data while it isn't running on Android either, but I'm being facetious to take it so literary. All background location data collection by Google on Android is opt-in. Similarly, Apple collects background location data on iOS if you opt-in.
Let's analyze how things appear from the user's perspective in both cases. If the user doesn't opt-in, the only difference is that the user saves a lot of money in one case. If the user opts in, one provides superior services with that data (e.g., location-based Google Now notifications) and results in more relevant location-based ads in addition to the money savings from the previous case. In both cases, the user is better off with the Moto phone.
You may have a better understanding on this than I do as it's been awhile since I researched it. With apple much of the location info is actually kept on the device where it can actually make use of it locally rather than sent up to a cloud dossier on you. Google works very differently.
Opt in is a little disingenuous in both cases. If you choose not to opt in you basically have an expensive brick. The challenge really in both cases is that you have no idea what is actually being done with your data as the privacy policies of both companies are weak.
Primary point being is that if you look at the business models of these companies one is dependent on data collection and ads while the other device sales. Based on that I can infer what may be done with my data.
Your understanding is incorrect. Apple also allows opting in to their AGPS service, Find my Friends service, etc.; each of which implies sending location data to Apple.
If you don't opt in on Android, everything that doesn't require background location reporting continues to work. You lose no functionality compared to not opting in on iOS.
You can look at the privacy policies and learn that neither company divulges the data to other companies. In both cases, opting in provides exactly the same loss in privacy (to the company the device talks to). The only difference is that one provides better services with that data.
To your point, however, they still collect quite a bit.