I have a feeling the dropship was designed with the purpose in mind of combining it with the AT-TE, but they decided to add a walker with the set and figured they couldn't just release the AT-TE with it, and instead chose to design an AT-OT.
I am the brain, that which keeps you sane
I think your thoughts, I feel your pain
I am able to control both body and soul
I am never asleep, and I make you whole.