It's true that Adobe didn't develop ePub -- it was developed by the IPDF. However, Adobe is one of the largest technology companies involved with the IPDF, and I think it's fair to say that they had a fairly large role in steering some of the decisions that the IPDF made. But again, they didn't develop the format themselves.
As for the credibility of Engadget, to me it's always seemed like a site run by fanboys that just happens to have a decent budget and a large company standing behind them. But that still doesn't mean that their "reporting" is particularly accurate.