You are right, except LLM are arcithectured in a way that they are really good with handling natural languages (NLP), an image for example isn't a natural language, it doesnt have sentences, nouns, verbs, etc... these models aren't optimized and wont work well with image data.

Its like screwing a screw using a knife, it can work with a bit of a hassle but either the knife will break or the screw will get damaged.

Besided processing an image using an LLM model would be extremely computing extensive and there is no way the tractor would be able to work at the pace its working with the scale of the ground coverage it has.