I'm new here and hope not to step on toes in my first post. I've read and tried to pay attention to the topic over the years, Joel's question about older copies of the wood handbook had me checking my '55 copy. Nothing there about a season for seasoning.

A couple of things I noticed in the thread though that I can help with. Wood dries fastest in warm weather, 90 degree air even at high humidity has more capacity than dry cold air. The molecules are more excited about moving to new and exciting places when they are warmer too. There is an average air drying rate chart at the Forest Products Labs website somewhere.
I would bet they would answer a Q from the guild with a good response.

A start in the winter can often get the surface dry enough during cold weather to avoid bluestain and bugs come warmer weather. The slower surface drying may help with checking.

Sap does not go down, it may stop flowing but it does not overwinter underground. A broken water column is an embolism to the tree it cannot be re-established, that tissue is dead.

Conifers grow year round, thats why they keep their needles. They do grow painfully slow when the conditions allow in winter. The moisture content of some hardwoods is higher in winter, no transpiration from leaves.

One possibility I see is the change in starch and sugar content through the seasons, although that would seem to just trade one bug for another.

The general wood industry line is that it makes no difference, and I tend to agree. If time of harvest does have an effect I think it would be minor compared to proper piling and protecting the wood.

It would be neat to read the old report though.