As far as I know the only extant neolithic posthole with a large wooden post still in it we have seen is that at Seahenge. The central posthole was surrounded by a timber fence that was also still there, as are other ones such as at Holme II.
And the main feature of this posthole was that the hole contained an inverted tree.
In an idle moment I wondered what Woodhenge would have looked like if it had consisted of a magical upside down tree copse. I rather like it or I think I would have liked it.
I have just read the 2004 book Stonehenge and Avebury The World Heritage Site by Rodney Legg which makes the same suggestion. Apologies to Rodney that I hadn't spotted his prior suggestion.