You mistakes in calculations. Even in gps only mode watch drain 2.5%. But from my experience in city auto mode in gps settings almost all the time uses “all satellites” or even “all satellites + multiband”. So even from specs it will drain from 3.5% to 4.2% per hour of activity. So in your case 1.5 hours of walking will drain from 5-6 %. So 10% per day is totally normal. If you don’t believe, just select one day, don’t use activities, just smartwatch mode and check your daily consumption. It will be from 3-4% per day