I think I mentioned this, but this is normal for Waze... It never showed in iOS10, but if you're not actively in a point-to-point navigation, it STILL does track you in the background unless you kill it... same for me for years. it's nice because it still alerts me to things if i go out...
Even though you can now set all apps to "only while using," Waze still hangs on even if you aren't actively navigating, (not sure how they got away with that one), but Waze has a "sleep mode" so if you enable that before exiting out it will let go of the GPS antenna.