The complete Betsy Ross tale is likely an apocryphal story. There's no evidence that she met George Washington. Being an upholsterer, it's likely she did make flags, so the five pointed star story carries some weight.
Congress did not specify that particular flag. It only specified the general appearance. Another "official" flag of the time had alternating rows of three and two six pointed stars.
What Nike overlooks is that condemning a single flag of the United States condemns them all. They are all symbols of the Nation. This is why older flags are still flown next to our current banner.