Don't be distracted by what "tricks" a magnetic sling can or might do. That's not the issue. Any discussion about "tricks the magnet can do" avoids the core issue being discussed regarding the slings core function.
Focus on their core function. The function of a "sling" is to put the ball back up the playfield, and possibly into the out lanes to end the ball.
The slings are not really an issue during single ball play. If the game had NO multiball, then it wouldn't be an issue.
But this game has multiball. So here we go...
If the slings are active 100% of the time (required to do their core function), they will impact multiball significantly.
When ANY ball hits EITHER sling, ALL BALLS near the magnets will be thrown in the direction of the "pulse(s)".
That means, balls NOT contacting the slings, NEAR the magnet, will be as if they did hit the sling.
Even if you wanted to use code to turn off the slings during multiball, that would make the slings "dead" plus, no magnet related functions would work at all.