Growing up in rural Ontario, I've seen plenty of these, but I was always given a different explanation for it: chains stretching.
The idea was that these concessions were laid out via teams with two sets of horses pulling a chain directly west, then when the chain was fully stretched, putting down a post to mark the point at which the concession ended, tying the chain to it, and pulling the other end ahead until it ran out again.
This worked, but if team A has the old chain, and team B has the new chain, team A will keep being a few inches and then feet ahead of team B, who are working a few miles to the south, because the chain started to stretch over time.
In hindsight, I realize now that I have no idea if any of this is even remotely true, but it was a plausible explanation that I'd heard from a couple of sources.
The idea was that these concessions were laid out via teams with two sets of horses pulling a chain directly west, then when the chain was fully stretched, putting down a post to mark the point at which the concession ended, tying the chain to it, and pulling the other end ahead until it ran out again.
This worked, but if team A has the old chain, and team B has the new chain, team A will keep being a few inches and then feet ahead of team B, who are working a few miles to the south, because the chain started to stretch over time.
In hindsight, I realize now that I have no idea if any of this is even remotely true, but it was a plausible explanation that I'd heard from a couple of sources.