Answer
IBM's S1112 limitations page says the server supports a maximum of four IBM i logical partitions per server. IBM also notes that if you assign more than one virtual processor to an IBM i partition, you may be able to define or activate fewer IBM i partitions at the same time.
That matters because the partition count is tied to the same four-core IBM i boundary. Buyers should design the partition plan and virtual processor allocation together instead of assuming "up to four" automatically means four equally sized production-ready partitions.