It is also based on the simplistic assumption that nationality is determined solely by country of birth.
What if you moved to the US where your child was born and raised to be a passionate England fan. They've supported the England national team, and become good enough at sport that they get to choose between the US and England - they choose the latter, despite never having lived there. Isn't that their choice and how it should be?
Whilst some of the Wales players no doubt supported England and would have chosen the England team given the option, there are others who will have been born in England but identify more with Wales.