So arabs would have a 50% increase in trunout while major parties have a 20% increase and chareidi have a 12% increase? (I know these don't match exactly to your example but are a very rough estimate) Why would we make such an assumption and what does this have to do with his statement?
The reason I'm making though extremely rough assumptions is because if we're looking at an overall increase in the participation rate it needs to come from somewhere. It's much harder to grow a participation rate from 70% to 80% than it is to grow it from lower starting numbers, there are just more non-participants that can be converted to participants.
Now if the 10% increase is across the board, then in absolute numbers it favors those with a larger starting baseline. A 10% increase of 7 seats might still run short of 8 seats. But a 10% increase of 32 seats is likely to gain a few.