Creating slots in the biscuit for the fletching to pass through will also compromise some of the arrow centering attributes of the rest and lessen its reliability. I would not do it. On a tuned bow the old black biscuit might have cost a couple FPS and some minor fletching wear. I'm not seeing any speed loss or fletching wear with the B-2 biscuit and don't even advocate trimming with the B-2.
Exactly! The whisker biscuits attributes is removing the need to worry about fletch contact (usually one or two fletchings hitting somewhere on the rest) by having all fletches contact at the same exact time every time.