Less than or equal to(!) -- this is crucial, otherwise you would count every square of a prime number as prime.
I agree that there is no need to improve it if it satisfies your needs. But switching to the square root is not a factor of four, we're talking orders of magnitude and a legit asymptotic benefit here. It's not a very special improvement either, it's fairly common to write even simple implementations using the square root as the bound. So yes, for the first few hundred primes it should be practically irrelevant, but I believe that with technical algorithms like this, at least showing what impact little details can have is important.