Failed out of a maths degree and now shitposts about linguistics on the internet here. Those groups are all incredibly closely related to the point of speaking mutually intelligible languages and the map in the link you included directly disproves the point you’re trying to make.

Imagine claiming any knowledge or background at all and thinking a neutral observer in the early Middle Ages would thing an Angle and a Frisian were anything other than identical. It’s like claiming Gloucestershire and Warwickshire are entirely segregated ethnocultures.