Tom, you need to stop attacking this strawman. You're comparing apples and oranges in what is being discussed. You keep talking about it computing the distance from you to point B, and then how it's inaccurate when walking those distances. Well, when you walk those distances it's no longer simply a discussion of calculating the distance from point A to point B. It's calculating the distance from point A, to point ZZ, using points A, B, C, D, E....WW, XX, YY, ZZ. Each of those points taken based upon a location at a particular point in time with a percentage error, based on the device used, for each point. What you *should* be comparing, is the distance a GPS system gives between point A and point B, and then comparing that to the distance said wheeled device gets. That would be an accurate comparison between the two. Or better yet, plot a route using your GPS, see how long it says it is for distance. Then drive it and compare both odometer, and GPS final distance given. This will show you any error in the calculated distance, as well as the known error in the tracking distance. This also answers why professional grade equipment will have a more accurate distance measurement, because the error in location is lower, and thus there is less error between each point from A to ZZ. The software used will also have an impact on this, with your phone GPS using understandably less expensive (and thus less precise) software.
It's absolutely fascinating that you can keep referencing and sourcing that article, but disregard every bit of information it provides about higher accuracy mapping it provides for some reason.