That would be a valid argument if the GP was a physicist, I guess. Why should GR be a prerequisite for CS?
The problem for the poster above is that if you read SICP outside MIT or especially outside college, you're not surrounded by a bunch of science nerds who can be persuaded to explain general relativity in return for beer and a pizza. If you're not swimming in a sea of science, then problems involving the behavior of fish seem much trickier to solve. I've seen this problem iwth a few other MIT books, eg Horowitz and Hill.