Phones often rely on a combination of GPS and cell phone tower signal, and their accuracy is improving each year. I can guarantee you that if I went there with a 2021 model phone and took the tracks, there would be greater error compared to a newer model.

That is how science works. You try to replicate data, and the more data you have, the more accurate your results. In some spots where I had to backtrack and there were minor deviations, I took the average of the two lines. 

I don't see no other GPS Traces, so there is no other data to compare it to. 

And again, you need boots on the ground. 5 years ago it might have been a 6 foot wide gravel path, but if vegetation starts to grow in you will start to have some weaving. I don't know the specific sections you are talking about.