It's a theoretician's trope. "Identical and spherical" is the baseline state of the objects in a system one wishes to model. There's are several jokes with this as the punchline.
An executive is retiring. He's been very fond of horse races, but has been very responsible throughout the years. Now with some free time on his hands, he spends more time than ever at the tracks and collects large amounts of data. He takes his data, along with his conviction that he's certainly onto something, to a friend in research at a nearby university. He convinces his friend to take a look at his data and find a model they can use to win at betting. After many delays, and the researcher becoming more disheveled over months of work, he returns to the retired executive to explain his model. He begins "if we assume all the horses are identical and spherical..."
That author uses it to mean “model”, as he calls a variety of programming models “spherical cows”.
Well, for sure, a core tenet of computer science is that all models of computing are equally powerful in what inputs they can map to what outputs, if you set aside any other details
An executive is retiring. He's been very fond of horse races, but has been very responsible throughout the years. Now with some free time on his hands, he spends more time than ever at the tracks and collects large amounts of data. He takes his data, along with his conviction that he's certainly onto something, to a friend in research at a nearby university. He convinces his friend to take a look at his data and find a model they can use to win at betting. After many delays, and the researcher becoming more disheveled over months of work, he returns to the retired executive to explain his model. He begins "if we assume all the horses are identical and spherical..."