No, you misread. The complexity increases when a user only sends from one key pair and receives with another. This makes it more difficult for snoopers.
Ah, we use the same key-pair to send and receive, it would be better if we used one key-pair to send and one key-pair to receive.
It is pretty cool to be able to send messages that are encrypted and immutable by using private keys without having to trust in or need for a third party.