Slinky have you actually gone and seen the work?
Perhaps before people hang ol Digger out to dry with negative comments about his choice of materials and technique on a couple very small sections of trail they actually inspect it for themselves.
I just went and looked at it. There are three specific sections with concrete. Two new and one that was done earlier. We didn't hear any grumbling when Todd used concrete to salvage the very worn out log into the teeter.
I am betting that Todd has had to rebuilt the other two sections numerous times in the life of the trail this use of concrete would be an attempt to built something that won't need to be rebuilt numerous times again over and over.
One section you will always know is concrete the other as it weathers a bit and with some sprinkles of dirt a rider might never know it was used.
Ps the trail is closed right now so anyone going to look please plan in hiking.