Thrawn is a bit too heavy to make use of such a maneuver, but he does have some skill at free-climbing, and with the way debris is stacked -- and the ways in which the walls crumbled -- he manages to find enough toe- and footholds to make it work.

He'll also enter the vent feet-first, because he fully expects that Hera will attempt to render him unconscious, perhaps with the droid-head.