5 blade vs 7 blade clutch fan

Two comments-

The offset blade also allow room to get a hand and wrench in to install the fan and other things.
You absolutely could not work on the front end of my Dakota without the offset.

Not sure about automotive fans but statistically, a four blade home ceiling fan moves more air than a five blade fan. Sounds non-intuitive, but it's true.

IIRC the same applies to impeller blades n water pumps- the high capacity ones have fewer blades.