Ah, I gotcha. It's not a direct quote or anything, it's a vague memory of something some guy said. Since the brand manager of D&D seems to change annually I have no idea who's responsible for making public pronouncements, and this being the internet, the guy could have been someone else easily enough. Or I could be misremembering who said what in the thread--it might well have been a development employee or even just a poster extrapolating from something Dancy or Ryan had said in years past. If I had an easy way to go back and link the statement I would, but ENworld lacks search, and anyway I doubt I know enough to find it if they had one.The way it was said, it left the impression that 3rd party companies didn't produce enough adventures. Which is wrong. Both, Necromancer Games and Goodman Games, had a strong adventure output during the time the statement was made.
On the other hand, "3rd parties not living up to their expected responsibility" doesn't really mean they didn't produce enough. It just means that a certain expectation of WotC was not met. I guess they expected people to buy 3rd party stuff. Instead, their customers were calling for "original D&D" adventures. This means that, IMHO, this is actually more a statement about WotC's own customers than about 3rd party vendors.
There is no dishonesty involved. It's just a clever way of expressing the state of affairs without blaming your customers, plus to give an explanation for a sudden 180 degree change in publishing policy without having to say that you don't know what else to put into the publication slots.
I kind of doubt that there's one uniform sentiment at Hasbro about the issue. The claim that others weren't supporting 3.5 with as many adventures does appear to be true to me, but you don't think so. I can't think of a good and convenient way to check, so I guess we'll just have to disagree about whether there are as many 3rd party publishers of adventures now as there were (or were expected to be) before.
If there are fewer 3rd party adventure publishers, it would appear to make business sense to produce adventures in-house, assuming Wizards still believes that adventures drive the sales of more profitable products, while being a cost-sink themselves.
If they no longer believe that (and they might not--there's that management change, again) then they might have decided to start releasing adventures just for profit, though given the number of creative new sourcebooks in recent months, I doubt they needed to in order to fill a hole in the production schedule. Though I guess there's the cross-promotion angle, where you can use stuff from new MMs, the Complete series and so on that aren't in the SRD, and thereby drive sales of those items in a way the competition can't.