[Not another shrubbery]

Originally Posted by Daigoro

We considered that, but it first says "with appropriate Move," then later says "in other respects treat this as Insubstantiability." We read that to mean that you don't get the movement aspect of Insubstantial.

Kromm clarified this in a PM to Der Wanderer, who relayed it in the thread Injury Tolerance (Diffuse, Swarm), here. Flight is supposed to be the default assumption for Swarm... crawlers and other land-bound hordes should take a limitation.