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I'm on Android 6.0.1 The trouble started when I installed Uber and Lyft. I don't know which one screwed the pooch, but now when I turn on Location it immediately goes to high accuracy. Previously, the behavior was to challenge with a question: Improve location accuracy? And the options were Disagree and Agree.
After looking around, I noticed developers talking about an addAPI call in Google Play Services. So on my LG phone I went to Settings/Apps, clicked on the ellipses menu and selected Show system. Went to com.qualcomm.location.XT, clicked on Storage, and selected Clear cache, and Clear data.
Back to All apps, continued scrolling down to Google Play services, clicked on Storage, then Clear cache. Then, clicked on Manage space. From there, clicked on CLEAR ALL DATA. Note that this action might adversely affect your experience with other things - I don't know, I'm not a programmer or very well versed with Android OS. But I don't care - the auto assignment of High Accuracy to the Location service is supremely annoying.
Once these steps were completed, I waited for about 20 seconds, and went to Location. Turned it on, and voila, the Improve location accuracy? question popped. Needless to say (in my case) I chose DISAGREE
Hope this helps you too.
Cheers.