WOW. It has been taught in audio classes for decades - DO NOT PUT 2 CENTER CHANNELS IN!!!
This causes comb filtering. Which is bad! If you think you don't hear a difference, you haven't demoed it (A/B) to yourself to hear.

Brendon,
I know you use to have a good 2ch setup at your house. Do you have something setup you can play with this, to see for yourself. Especially listen how the sound changes dramatically from seat to seat with 2 centers installed vs. 1. If you have an RTA, look at the comb effect it is creating to the response.
I promise you, you will never mistreat a customer by doing that again.

And I have seen several dealers do it, just to sell an additional speaker. Knowing full well it was wrong to do.