Something changed but IDK what without digging really deep but I suspect the ammo canister. IIRC that had a code change at some point so it could be loaded into a vehicle (... maybe) and was given min carry cost that does not show in the OOB's. As far back as I can check it has 1 'crew' ( everything has to have at least 1 crew even ammo ) and 0 carry cost but in the initial scenario to start that campaign it reports a carrying cost of 4
Another case of 'reality" bumping heads with 'game reality. The combined carry capacity of those mules is 45 and the units they have to carry weigh 40 but unlike reality, we can not break down units to spread out the weight.
The problem is the simple solution of increasing the mules carry the capacity to carry 10 which would solve the problem does not work. I have tried it and the start-up scenario still only shows 9
That said
IT IS possible to get all the units in the initial startup scenario that are on foot onto horse or mule transport. It just requires a little bit of creative re-organization
Every unit is loaded
HINT.... load the HQ and E6 ( aamg) into the same cav trasport unit.
It's possible to load all foot units onto the mules and horses and have one team of horses not loaded