I think the right way to explain it would be that it gets more precise, but not more accurate.If you click the track does it change?
So in the picture above, if I click on either track, I see more detailed twisting and turning. And I think that each of those turns is approximately correct. Like when it shows I've veered a little bit to the right for 3 yd, I probably did turn a little bit right there.
But those two tracks are still about 30 yards apart. When I made them, I was walking on a fire break that's maybe 10 or 12 ft wide. I didn't deliberately walk down one side and up the other. (I probably mostly walked right back over the same ground because it was the easiest or quietest place to walk.) But even if I had, there's like 80 ft of variance that's not explained.
Editing to add: So I think whatever in this phone is sensing me turning or speeding up is doing okay. But my first guess is that the actual geolocation it's starting from is off.