How does that contradict what the author said? His argument is that any field closed over itself, over time, will tend to distance themselves from reality - obviously, the initial impetus of a field happens far too early to experience such effects.
I am saying that whether or not science and engineering are tied to reality has little to do with being relevant to the commercial world.
My claim: influence of commercial world is extremely unimportant for most of the important parts of Field X, ergo, commercial influence has had almost no bearing on keeping Field X "useful", regardless of whether or not Field X is actually useful.
Statement to support claim: the vast majority of what we consider 'science' (lumped in with engineering by the author) consists of a theoretical backbone tested against reality, which has nothing to do directly with commercial interests in theory, and often in practice. Examples include mechanics, EM theory, quantum mechanics, relativity, genetics, number theory, integral calculus. You would have a hard time proving that these things, which all have a basis in reality, are that way because of "crass commercial necessity", as the author claimed.