I find that pretty bizarre. I do sometimes refer to more than two things as "a couple of X" (which I probably immediately internally cringe over after saying it), but if I were to ask someone to buy a couple of something, I would never expect more than two to be bought.

Ultimately we probably should just avoid using these words when asking someone to do something that will result in some sort of concrete number of things or events. Better to just convey a specific number and avoid confusion.