The 572 Indy engine that Best Machine built for me a couple of years back dropped the sleeves. I never talked to Chuck about it but I assume that the block came from Indy with the sleeves installed. If so, then Indy might have the same issue with sleeves dropping. If you're buying an aluminum block it makes sense to ask the vendor about the sleeves.
On the flip side, we've run a ton of aluminum Chevy engines over the years and never seen a dropped sleeve. So maybe Dart and Brodix and others have it figured it out?