Aluminium has a higher expansion rate than brass so the idea of a quicker break in is more by a higher expanded sleeve.

The wear has nothing to do with the aluminium sleeve because it is hard chromed so there should be hardly no wear on the sleeve unless the chrome is not that hard. Chrome plating aluminium is a bit difficult and so a different chrome could be used.
But because the sleeve expands more you can imagine that temperature changes can have an effect on the pinch zone. that can cause the wear.

But aluminium is a good heat conductor so you can run engines cooler or looking from the other side: leaner to run the same temps as with brass.