BTW, what would be the story behind units recovering most when suffering from casualties early in battle? Someone who got wounded on the first engagement and is bleeding for hours before he can be helped will certainly not be better off than someone who is wounded in the last moments of the battle when the enemy is already on the run and medics and helpers can enter the field.
It makes no sense at all!
However this information will change my battle tactics. I will try to engage the enemy first with the units that have to travel the furthest away to get retrained. For example in my Makedonian campaign, when fighting Ptolemies in Egypt I'll try opening the battle with my Thraikioi Peltastai since the are trained in Thrace, instead of my slingers who can be recruited everywhere.

So the class of the unit that suffers the casualties has nothing to do with the recovery?