I guess I'm wrong about that then :). My assumption was based on the fact that when I traveled into areas with no data coverage, I distinctively remember Google Maps having great difficulty with cached map data, while Apple Maps didn't.
(In the hotel prior to driving I would load both maps and directions in both apps, "click through" the directions to give the apps a chance to cache the data, and then go on my way - if I dicked around in Google Maps it tended to just not show anything, or a very very fuzzy view of where I was, whereas Apple tended to show a low-precision (but clear) view of where I was.)
It seems to me Google Maps would have to preemptively request permission to access local contacts because it wouldn't know in advance if a particular search should match a contact. And some people might be confused by the unexpected request and not understand why contact search isn't working later (or be confused if they disabled Google Maps' contact access because they didn't make the connection).
I can certainly see how, from Google's perspective, it seems cleaner to use the contact store they know they have access to and is presumably the same one they'd use on other platforms - promoting consistency. Is that ideal for every user? Clearly not. But, in the spirit of the original article, it is probably the way to get contact search working with minimum friction for most users.
If it used local contacts and I had denied it access when it asked on the first startup, it could instead display a message saying so, offering a button to click to request access to contacts again. It would be strictly less complicated for the user.