That's a classic tuning procedure (boattailing) to relieve gas exchange or breathing between the cylinders and the crankcase (volume below the piston). According Bruce Anderson 10 more hp for a 2 liter engine. This needs also machining the crankcase like this which correspond (red) to the slots in the cylinders:
I do not have seen any dyno to proof, but because I don't see any downside except the work it's worth a try