Spadework. The digger would do all the bulk, and the spade would do the trimming, with the help of a human on the other end. Same as trimming a trench or footings. All clever stuff.
but at the same time not disturbing 1million year old bones and pots....
i've dug a few holes in my garden in my time and i know sometimes there'll be a huge rock where you want to dig, or you'll tread on the edge and it will break away..... they do a good job