It is not really a "mistake" -- if you are redeeming BAEC miles, then you are subject to any system/date range limitations of that programme (in addition to the Award Availability itself).
The "reality" is different for the numerous FFPs that support redemption on EI -- in your example, there would be no point in enforcing the BAEC (330-day) "reality" on QF FF members (whose "reality" extends to 354 days).
So you're saying that the 330 day limitation is a BAEC limit? The guy was quite happy to book me LCY-JFK BA flights at 339 days, and he said that they shouldn't have any limit other than those provided by the airlines...