From the looks of this discussion, it looks as if I'm not the only one who's
confused about the difference between "coincidental" and "matching."  But
even if there is some clear definition that differentiates the two terms,
can anyone explain to me any rationale for treating them differently (i.e.
why one results in a 4x4 and the other in a 5x5)?  There is no reason that
they HAVE to be treated differently, so why are they?

Clay