People who reported getting their BOWP despite the four-month rule usually had some kind of hardship, with losing their job through no fault of their own and other factors. And either the VO was sympathetic to this, or perhaps they were caught napping and didn't check all of the criteria.
These cases were mostly before OB485a (September 2013) which restated the four month rule in more explicit terms. Whereas before, the rules said you are eligible if you have four months or less on your permit, they now also say that you are not eligible if you don't have four months or less on your permit. Obvious perhaps...
Really the BOWP was designed to spare everyone the hassle of a new LMO application, for people who were approaching the end of their LMO and likely to become permanent residents anyway. It wasn't really intended to help people change to a nicer job