It's point to point addressing (/32 netmask). Instead of using traditional subnet for the link, which would require at least four addresses (network, device A, device B and broadcast for /30), you can do it with just two. Device A gets one and you tell it the second one is on the other side of the link. And the other way around. And it works.
Reusing the address from subnet on the other interface is not necessary part of it. But as you see, it can be done. They probably felt really strong need to save addresses.
Also the screenshot is from some older RouterOS, current one no longer has broadcast field. But that doesn't really change anything.
People who quote full posts should be spanked with ethernet cable. Some exceptions for multi-topic threads may apply. Not intended as incentive for masochists.