Yes it's sandbagging and yes, it's rampant in the APA and has been for 20 plus years. It's why folks join due to the lure of Vegas and play for awhile then eventually leave and find other leagues or weekly tournaments to play in.
NAPA has a much better handicap system that eliminates sandbagging and BCA has one that is close. It just takes some folks time to figure it out for themselves. It's accelerated sometimes when folks realize that other leagues like NAPA and BCA have great Nationals as well, not to mention they're much easier to get qualified for.
APA has spend a lot of years looking for ways to divert attention from the problem of sandbagging and has implemented other things like the reduction system they put in back in the 90's which is also a double reduction on the 7's (why penalize your best players?) and more recently the 3 point scoring system which also penalizes the upper half of the skill levels in the league by giving a point to 2's, 3's and 4's for winning a single game and making it to the hill.
The funny part about sandbagging is it's still only a temporary thing because the scoring system for APA takes into account wins and adjusts your 'innings' accordingly whenever you win, giving you a minimum score. The problem, however, is that the minimum score takes time to have an effect on your handicap so the sandbagging is still prevalent for a very long time before it's caught up with in the system database.
APA is just a mess when it comes to handicaps and needs completely revamped but every amateur league wants their own stamp, or twist on how the amateur game is played so they've stuck with theirs for far too long. Vegas is great, I've been many times on APA teams, and you don't need to sandbag to get there. It's hard to win against the teams out there that do, though. A lot of teams end up losing to teams that sandbagged to get there and eventually will get raised up or dq'd out in Vegas but then, the damage is done and good teams have been beaten out. It's sad.