I don't think that notion is controversial. It is noted in the Wikipedia article: [en.wikipedia.org
The fractional term 256/81 approximates the value of π as being 3.1605..., an error of less than one percent.
Specifically, problem 48 explicitly reinforces the convention (used throughout the geometry section) that "a circle's area stands to that of its circumscribing square in the ratio 64/81." Equivalently, the papyrus approximates π as 256/81, as was already noted above in the explanation of problem 41.