You cut off the rest of the sentence.
"The act of deliberately avoiding any and all conflict"... "so that one may make the game unplayable".
The game is still playable. It is possible to beat planking. It's just nearly impossible with some characters and much easier with others. IMO, it's no different than allowing DDD's infinite.
I thought it very likely that argument was coming next, but i left off the rest of the sentence so you could go ahead and make it first.
The problem here is your interpretation of the word "so", because that's not exactly what the word "so" means. "so" means "in order to" or "with the goal of". For example, "I bought my mother a golden necklace so she would be happy". Even if my mother became sad, the sentence is still true. That's why i bought the gold necklace, that's what i bought the necklace "with the goal of".
When one planks, he or she does indeed do it "so that one may make the game unplayable". That's the idea, if you are playing ganondorf i start planking so that we don't exchange any more damage for the rest of the match, because i'm already winning. That's my goal.
Now i probably won't reach that goal. The ganondorf will have to jump down, get smacked, and die, trying to stop the madness. It just like the gold necklace thing though, just because one doesn't reach the goal of the "so", doesn't mean that wasn't the goal in mind.
See, the "so" phrase is there because there are two conditions to stalling. One must be doing something that a. avoids all conflict and b.
desires to avoid all conflict. The example given, moving across stage for a better position, fulfills the first condition but not the second, and that's why they had to put the so phrase in. Because this interests me, here's some actions protected by the so phrase:
-Charging the laser and gyro while ledge stalling (the goal is charging the projectiles)
-Ledgestalling until the Shy Guys come because you hate Snake's upsmash
-Ledgecamping for damage
-Ledgestalling while your other pokemon recover from stamina
-Even, in fact, ledgestalling for five seconds and getting back onstage because you like to screw with people. (I think in tournament it would be pretty clear how long is "screwing with people's minds" and how long is "the clock.. keeps.. ticking")