I think what's often missing in these "matching doesn't matter" discussions is the reason we use a center speaker in the first place: so that listeners in off-center seats have a good experience, too. And for those off-center seats you want a wide-dispersion center speaker, which is hard to do when physics constrain the horizontal dispersion of your horizontal speaker. I think too many people are fixated on the on-axis response of the center speaker. That, I think, is not very telling of the speaker's performance in the context of why we bought it in the first place (otherwise we would just be happy with L/R speakers and sit in the middle seat). For example, look closely at the 30° and 40° lines in yellow and green, which is roughly where your off-center listeners will be. Everything might be all hunky dory for you in the middle seat, but I dare you to tell me these two speakers will sound the same in the other seats.When someone says mismatched centers don't matter what they really mean is that mismatched centers may not matter to some but will to others. We don't all have the same auditory capabilities so the degree to which we will notice a mismatched center varies. An obvious example is that a few people have perfect pitch but most don't. Try to tell everyone that exact pitch isn't important and those with perfect pitch may tell you that even slightly off pitch is not only noticeable but can be annoying.
For those with more sensitive auditory capabilities a mismatch in speaker voicing can be noticeable and even annoying. So the most important thing when considering audio advice from others is to self-analyze where we are on the auditory sensitivity scale. The different advice others are giving may or may not be applicable to us and it's up to us to figure out which sometimes conflicting advice best matches our hearing.
And yes, I realize the OP's goal was audio for himself only. But this needs to be said because it comes up again and again.