I have always taken the satnav routes with a pinch of salt. Every single nav system that I have owned in cars for the last 20 years has tried to take me down a cut-through footpath (we call them jittys in Leicester but might be one of those dialects like cob/batch/roll). It has never been a road but the mapping source that all navigation systems seem to use obviously think it is accessible.
what I have noticed however is that often when starting a journey the location is 2-3 meters out so the route gets a bit confused to start with. After a few minutes it does sort itself out but we often have a laugh with the kids when the nav is showing the car going through houses.
it does happen mid journey as well sometimes, especially when there is a parallel service road close to the road I’m on, and the navigation thinks I’ve turned into the service road even though I haven’t. Having watched it when I haven’t been driving it’s seems the navigation tries to be predictive with where you’re going, I assume using compass and speed/steering etc so it doesn’t need to query the GPS so often and so seems to think you’re going down a different road, and then a minute or two later it corrects itself.
i don’t think systems are charged for GPS use other than the initial licence so it might be a processing/responsiveness thing
for info I have the 14” nav system