The biggest problem is that stealth has always been surrounded by political demands all the way back to the first stealth aircraft. Given Sprey's target audience with the interview and the way he chose his words (particularly at first), I think it's likely that he was addressing the prevailing belief that stealth aircraft are invisible aircraft. That said, you've hit the nail on the head in terms of the difference between being stealth (re: invisible, such as what Sprey's railing against) and being low-observable.
Public comments about the JSF program by Lockheed, military spokespersons, and congressional supporters alike have all touted the plane's stealth capabilities to an extent that makes me wonder how many actually understand the difference between the two. Given the likelihood that operational demands (particularly close air support for the Marines with the F-35B... not that CAS missions could every be very stealthy) will make the entire point moot, I really don't understand all the emphasis on it.
