What is this shortcut meant to do in the Messages app?

When I use the Opt ⌥ ↑ or Opt ⌥ ↓ keyboard shortcut on the macOS Messages app, it places previous messages I've already sent into the typing area and cycles through them.

I often press these keys by mistake when trying to go to the beginning or end of a line, and wonder what this is actually meant to help.

What are these shortcuts meant to do?

Solution 1:

The shortcuts are just as you say, to cycle between prior messages sent in order to use them again.

Is is useful? Questionable. But it works exactly the same way as it would using Terminal, for example, in order to access prior commands again.