I am puzzled at what you mean by " ... during WWII ..." You seem, but do not express clearly, to think that it would be difficult to distribute nationally back in the '40's from a central location. I'd argue that it probably was easier for 2 reasons:
1) the national distributors had strong established networks for distribution because they carried so much news and magazine products that their distribution costs were low once spread over so much material, i.e., on a "per issue" basis, the cost was small enough to turn an easy profit per magazine (including comics) and
2) the rail system as we know it is only a shadow of its former self. Rail must have provided a very useful, efficient and geographically widespread way to get material cross country until local shippers loaded them on trucks.
Once you combine the two, printing in one location and distributing nationally seems like the best economical way to do business for the publisher since the distributor did the heavy lifting to get the product on the stands.
Also, recall that it was not uncommon for publisher to also be distributors. Heck, Charlton went even one further by being all 3: publisher, printer and distributor. Talk about keeping most of the profit pie
World War II = WWII, just a time reference for a period when resources were scarce. I admit I've got no idea how the printing industry operated during that period. Seems interesting, though, and I'd think it would have had a significant influence on comic distribution and availability at the time. The railroad makes a lot of sense and puts some good perspective on the whole issue.
I guess this generally means that there probably are issues where color quality is poor throughout. Makes it more interesting to see if you can find well-colored copies of all the issues.