This is a known issue and a side effect of terrain reversion. A proper solution is complicated and wasn't working out at the time.
At the time of the terrain reversion patch, my choices were:
1) Have logs and bundles block reversion (as building do).
2) Move logs and bundles to match the terrain on public land (which makes them pile up as you reported).
3) Completely decay logs and bundles on public land as soon as the first pass of reversion occurs. This would clear up a lot of piles, but also remove road markers placed by players.
Based on player feedback at the time I chose number 2 even though it stacks up piles. This allows player to continue to mark roads with logs and players at the time said that for the most part piles of bundles were not being left on public land. (Of course this does cause issues with abandoned tribes).
I need to find a better solution and now that I've fixed some collision and placement functions with the architecture update, a solution should be easier to reach.
Just to make sure, this is happening only on public lands, and not tribe lands, correct?
I hope that answers your questions. This will be worked on.
Thanks!
Note: Additional information posted in duplicate reports
here and
here