Why do people assume a sparting partner is going to be 100% mirror of opponent?

[TyrantT316]

Whenever I hear people complain about chosen sparring partners, it shocks me that many complain.

You'll really never find a sparring partner who is as great or is 100% like your opponent. So you bring in guys that share similar qualities (whether one quality or five).

Or you bring in guys who can somewhat imitate your opponent or give your fighter a good sparring session.

Mayweather isn't going to find Pacquiao B and Pacman isn't going to find Mayweather B.