Removing the cans will create additional space, but at the time when the piston will be nearing BDC to open the transfers the new space isn't very accessible - it's nearer to the bottom of the case. This may be compensated for by using a properly tuned exhaust. Because the primary compression ratio gets lowered when using one there is an additional small benefit - there will be a slightly decreased pumping loss due to the decreased pressure. This includes sucking in the mixture and pumping it out. There may be an advantage of a slightly cooler mixture as a result of the larger volume as well.
Turbulence is an interesting thing.
When you spin a propeller in water you can see its act very clearly. It makes things move around a lot. In a 2 stroke motor the volume of mixture isn't going to be sitting idle in the case so the crank can whip it up. The direction of the incoming charge is not towards the crankshaft counter weights, it is more inclined to follow the piston - going up. If I understand turbo veining correctly it is a modification which increases the volume in the crankcase by its nature as well.