All the good aluminum cutters have a lot bigger cutter edges on them and are further a lot further apart than the one shown in that picture.

Tell that to the 30 plus manifolds ive worked on and 11 sets of al heads and 8 sets of iron heads.

Just a personal preference that dont dig supper hard and leave a good finish without needing any touch up of any kind. Maybe one time an hour I might have to take 5 seconds on a fine wire brush or hit them with an air hose.

I know your old and wise Cab but there is more then one way to skin a cat.