“In Age of Empire 2: The Kings, Camels were only classified as Cavalry. However, upon the release of Age of Empires 2: The Conquerors, Camels got a 2nd classification which also made them “Ships&Camels” - Ships being the odd part. The community has always wondered if this was done because “Camels are ships of the desert” fun-fact, or if there was any balance purpose to it? Can you clarify what the purpose of this change was? Thanks.”
Oh man, I only barely remember this. Maybe one of my former colleagues will see this answer and speak up. I think it had to do with some kind of bonus damage. Camels in AOK were ant-cavalry. But because they were trained out of the Stable and we wanted them to benefit from cavalry upgrades, they were type cavalry. This made them good at killing each other - probably ridiculously good. Adding them to the “ships” type was probably a way to make them universally worse against something, like perhaps buildings.
Backing up a bit, the original Age of Empires and early Age of Kings had two types of armor: piercing and normal, and we tried to balance the game based on what kind of damage and what kind of armor a unit had. If you did piercing damage and had piercing armor, you would be strong against your own kind of unit. As our unit relationships got more complicated, our armor system had to get more complicated too, or we couldn’t handle relationships like camels being weak against everything but cavalry (not including other camels). For awhile we did this with even more varieties of armor and eventually graduated to a bonus damage system, where someone could just do 1.3 damage vs. certain types of units. Bonus damage let us much more finely-tune unit relationships, but it was much more opaque. You wouldn’t necessarily know that Hun cavalry did bonus damage to building without knowing their bonus damage.
I am guessing a bit here based on knowing how the systems work. I could be wrong.