From: Santa Rosa, CA
First off, the vehicle issue was only a scenario data issue. This was reported in the 43-45 campaignwhere some reinforcement units were not arriving with vehicles. As far as we could tell this problem does not exist in the 41-45 campaign where reinforcements arrive with vehicles.
As for the manpower, my guess is that since you are bouncing around at a low armaments level, this is causing inefficiences in the replacement system so you are not using as much manpower as you could. That's just a guess though. Other explanations are that high levels of activity prior to mud left you with large numbers of damaged elements which are now returning to the pool but being in mud, it's harder to get the replacements back to the front. There is so much going on in the system that you have to expect a certain amount of friction. Once your armaments go up, and clear weather returns I'd expect you would see the manpower pool drop.
As for the total numbers, check each country. My guess is you have a few allies with 0 armaments and lots of men, and some with lots of armaments and no men. With the Germans low on armaments, there won't be a lot of armaments given to the allies, and the allies don't give them to each other.
All understanding comes after the fact.
-- Soren Kierkegaard