Are you saying you don't think the GPL forbids attempting to redistribute with reduced rights, or you don't think offering a contract which does precisely that (in exchange for trademark consideration) constitutes an attempt?
Separately, the GPL calls out that you're allowed to place a restriction on your distributed code when it comes to trademarks, in that you're not required to license your trademark. I.e. you're allowed to distribute code that's GPL-licensed but that it's impossible for people to legally use as-provided without either forking it or obtaining an extra license from you. v3 is a lot more explicit about this, but it seems implicit in v2 as well.
You could certainly take the position that any sort of trademark license containing usage restrictions at all qualifies as a restriction under the GPL, so your only choices are to completely allow or forbid usage of your trademarks without any conditions. I disagree with that view.
You've interchangeably described WPEngine's consideration under the contract to be "something", "stuff", and "behavior" – this vagueness seems to be dodging the issue: what specifically, as you understand it, would WPEngine have to give up under the terms of the contract Matt presented, in exchange for usage of the trademarks?