I think he's saying that inside of the loop in FizzBuzz, it should look like something like this (Python-esque pseudocode, assuming for a second print() doesn't add a newline automatically):

    if x % 3 == 0:
        print("Fizz")

    if x % 5 == 0:
        print("Buzz")

    if x % 3 != 0 and x % 5 != 0:
        print(x)

    print("\n")

i.e. no special "FizzBuzz" case for when it's divisible by 15, it just naturally falls out of the first two if's. It's a bit of a silly objection though, the it's fine to write it as the author did.

as I learned above you can use the "end" kwarg to avoid the newline:

    print("Fizz", end="")

That doesn't work here, though, because then you don't get "FizzBuzz" for 15 -- you get "Fizz" and "Buzz" on separate lines.

A lot of the rosetta code examples show the simple and the more complex example or less use of built-in functions to show they can express it with the core language.

Sure, but I think that's a different objection?