As I've been recently corrected on my knowledge there and discovered that it's more simple than I made it - Mech rating is used for Motorized Units, and Infantry for Non Motorized.
But that has opened up some questions on my end.
- A 'Motorized' Infantry (as per, temporarily motorized) unit what leader rating uses?
A Motorized SU supporting, or attached to a Non Motorized Unit, what leader rating uses? (Germany for instance can turn in a nightmare, with their non visible of yet leg / mot. Pionere units)
A Non Motorized SU attached to a Motorized CU will be considered Motorized?
Because I am sure I paid 0 attention to let's say Pionere Units or other SU if they were motorized or not, and attached them to some Mech 3 rating German leader in past games too for example. And it can be even more severe as a bucket of German artilleries are motorized and thus potentially fated to underperform badly.