I was fully prepared for the wet walls of the building to act as a reflector.

I'm surprised WiFi can't pass on reliably through branches. Must have been a nightmare back then.

I would guess that the interior of leaves are quite conductive and that this accounts for most of the attenuation and scattering.

Update: this comment on the original posting of this article suggests so: https://news.ycombinator.com/item?id=39896699