Seriously, have you read the OP? The optimizations in the OP do not prevent AR from asking for the same thing more than once. They do not effect how many times AR asks for things at all, as far as they can tell. It is _not_ caching database responses. It is caching internal AR calculations only, and does not reduce the number of times AR asks for things from the DB. Unless I am misunderstanding.
Not asking for the same thing twice (or N-1 or N^2-1 extra times) if has to go over the network is a good thing.
Databases often aren't properly configured OOTB, especially when it comes to temporary tablespace and query caching.