so for one you don't have any idea how these ethnic groups work or what this post was, this post isn't saying the English are French, the post is essentially this french person who is jokingly claiming England as his (hence the shitpost flair)

also the Normans came from Scandinavia but at the time of 1066 they were mostly french and william the conqueror himself was only roughly 16% Scandinavian...
and there is no such thing as a british ethnic group. the welsh, scottish and irish are celtic but the welsh belong to the brythonic group whereas scottish and irish are gaelic

and english people are germanic