I built a construction skid sign out of PT wood years ago and after one winter the wood touching the ground was 100% rotted out. A can of Krylon would have been a better moisture barrier than that stuff was.
I don't think the stuff was ever intended to sit directly on soil.. Even fence posts that are just planted in the post hole will rot out in a few years. The stuff is fine if used where it gets an opportunity to dry out. At one time it was a big thing to build basement walls (exterior) with PT lumber BUT they still applied a water barrier to the exterior surface.
