I can't defend either use, and don't really have much interest in doing that.
On the other hand you can see the original meaning and contrast in Iraq. I imagine the US Military and Iraq government as arborescent, or top-down, while the variety of resistance forces are rhizomatic, underground horizontally spread out and interconnected networks. Killing off various centers in this underground will have some effect but such a strategy can not succeed in wiping out the whole undergrowth. It will just budd new sprouts and reconnect in different pathways.
Unfortunately, there is nothing in and of itself that makes such an underground movement progressive---since in this case it isn't. Somewhere down the way, the Iraqis will have to get rid of both.
CG
^^^^^^ CB: The famous left organizational problem is the mirror image of this , or whatever. How could the Bolsheviks effectively defeat Czarism without an arborescent Party structure ? How could the Soviet Union ( China, Korea, Cuba, Viet Nam, et al.) defend itself against imperialism's arborescently-militarily organized attacks without becoming what it was fighting against ? How do you defeat the master without using the master's weapons ? Audre Lorde's Dilemma.
Venezuela may be coming up with a solution to this problem of all revolutionary problems: Get a arborescent leadership that uses its power to build rhizomatically , at least until the US attacks.
Leadership from the ranks is viable while the beast sleeps, but in general ,it is still a very perusuasive theory that the socialist state ( arborescence) cannot whither away until there are no longer any bourgeois states.