Yes Ernie. It is acoustics 101. Comb filtering happens due to all kind of conditions, including even when using only 1 speaker. Amazingly it doesn't sound as bad as it looks on an RTA, which would have you believe response is completely destroyed. Our brains fill in a lot of information (psychoacoustics) and with 2 ears on either side of our head, mic measurements struggle with properly representing what sounds get to our Cochlea.
That said, the detrimental effects to overall sound quality by rigging BS up is real. And running 2 center channels is definitely 'rigging' something up.

Correct solution is unique to each install.
Just having the stereo pair with no center, is correct if the primary seating locations are going to be near the equal distance point for imaging.
If seating is spread out, then some form of single point center sound anchor is needed near the video display.

And I love how the comments always come in: "It's just a living room system", "they don't care about overall sound quality", etc... Well in that case, it doesn't really matter what you do does it? Install 4 BOSE speaker in each ceiling corner of the room and call it a day.