I'm just guessing here, but I would think that we are looking at two things:
1) Confirmation bias. Unless there is an actual study showing that this is true, it may just be the snow weenie in all of us that remembers these types of changes.
2) But if the anecdotal theory is actually true, it might be that the patterns that result in an H5 feature going through the deep south may simply be more predictable due to the strength of the blocking required to make that pattern happen.