It seems to me (based on reported behavior), that Linux is special casing the loopback interface: when you add an address with a netmask to the loopback interface, it considers all of those addresses as local addresses.
As opposed to a normal interface where only the specific address is a local address, but the rest of the network specified are accessible through that interface.
Maybe one /8 wasn't enough addresses for you, so you added more? Doesn't seem like an unreasonable way to behave, even if it's different than BSD behavior; it certainly makes it easier to use lots of loopback addresses.
