This wasn't "marketing material", it was "technical marketing material", the stuff given to review sites, not the general public. And it was a relatively obscure portion that was incorrect, not something that most consumers would even understand, let alone care about. The technical marketing staff (a distinct group from the consumer marketing department) made the assumption that every enabled ROP/MC functional unit has two 8px/clock ROPs, two L2 cache units of 256KB, two links into the memory crossbar, and two 32-bit memory controllers.
This assumption was true for previous architectures (Tesla, Fermi, Kepler). It was true for earlier releases in this architecture (the 750 Ti and 980 were full-die releases, no disabled units; the 750 only disabled full units). This is the first architecture where disabling parts of the ROP/MC functional unit, while keeping other parts active, was possible. The marketing department was informed that there were still 8 ROP/MC units, and that there was still a 256-bit memory buss. They were not informed that one ROP/MC unit was partially disabled, with only one ROP and one L2 cache unit, and only one port into the memory crossbar, but still two MCs.
The point AT made is this: this information would have been figured out eventually. If Nvidia had been up-front with it, it would have been a minor footnote on the universally-positive launch reviews, not dedicated articles just for this issue. It only hurts them to have it not be known information from the get-go.
As much as it's hip to hate on big corporations for being evil, they are not evil for no purpose. They do evil only when it is more profitable. In this case, the supposed lie was less profitable than the truth. Therefore it was incompetence, either "they honestly didn't know this was how it worked when they sent the info to reviewers", or "they thought they could get away with something that absolutely would have gotten out, and would not help them sell cards anyway". The former incompetence seems far, far more likely than the latter.