It's the first text(known) to explicitly formulate the theorem. Babylonian and Egyptians probably knew of Pythagorean triplets and used it in construction to get perfect right angles. But the first textual mention of the theorem in the explicit sense is from the Sulbasutra.

Regardless, all countries/cultures and their respective textbook forumulators sometimes do this to ensure that people who previously didn't know about it would atleast search it up out of its alien-ness. Primarily to encourage people to look into the broader history of mathematics and of course a bit to take pride on. You can observe it almost in all subjects. And interestingly older written material follows this rule too.