It is conceivable that this has been purposely done to suit the Twenty20 format where the sixers matter more than anything else. By bringing in the boundaries closer, there are more sixes than what would otherwise have been easy catches. It also seems suspicious that so many sixes are getting hit, and that to soo easily, and not many catches at the boundary lines.
This, if true, is very disappointing. Its like the sixes are being manufactured!