I think fuel shear and relate it to making more average torque with a sharp lower angle than radiused to the 45 on the intake side as proven by darren Morgan and others. A cousin sister's brother's nephews uncle said he dyno'd and seen 20 foot pounds more average torque once he stopped blending it to the 45 and put a nice sharp lower angle. True story with humor injected.
what does the sharp angle do with the fuel when it hits it.
Let me take a leap and risk it just being my tunnel vision atm..
Quite possibly a back cut is a compromise with a slight increase in power to offset ..making it acceptable/desirable. Wish I could test