If he was paid in advance one lump sum, then no...the boycott won't help stop money going to OSC now. It should have an extra effect of making Chair reconsider working with OSC on future products. If there is enough backlash now about this game that they decide not to work with him again then he gets $0 dollars in the future. No future money at all is probably a better outcome than just diminished sales now.
Even though I'm trying to focus on one poster for the sake of having a consistent discussion, you bring up an interesting point.
Okay, like you said, the reason behind the boycott tends to fall apart if OSC was paid up-front, rather than percentage royalties. In that scenario, he's already received his money, the money wasn't coming from any of us, and any actual sales of SC go directly to Chair. So there, immediately, would be no concern at all for anyone's SC money being used by OSC for whatever his nefarious plans would be.
But now, in that case, what happens with the boycott? If the original motivation for boycotting the game was to keep your money out of OSC's hands, but OSC is actually out of the picture, financially, there is no reason to continue boycotting the game. So why continue the boycott?
You seem to be suggesting the boycott could be further used to put financial pressure on Chair themselves to drop OSC. Why? Chair was never truly part of your moral offense, right? As far as I can tell, the boycott was due to a fear of OSC. I'd wager that Chair really had nothing to do with it.
So why continue the boycott when it's truly going to only hurt the developer?
Further, would Chair even know why sales of their game underperformed? Would they even know of the presumed backlash?