I don't know if it's intentional or not, but all of Egyptian generals, when equipped with a chariot, have the same chariot model of light chariot, except when it's the main character using it, like Tausret who uses a better chariot.

I tried giving the chariot used as ancillary by Tausret to a general, but still it changes model to a light chariot.

Kind of not realistic when your general, an important person, is using a light, easily breakable, and cover-less chariot whilst the other lowly soldiers are using sturdier medium chariots.

The maximum weight of general's chariots is determined by culture. The actual weight is determined by the armour class of the general unit.

Egyptians can only equip light armour on chariots, Canaanites up to medium and Hittites up to heavy.

I presume this was a balancing decision to represent Hittite mastery of the chariots compared to other cultures.