Every language has it tricky or difficult sides - so does English.
The articcle does not really sound too serious about Old Norse and English.
In Normandie are non of the Nordic words left, but several of the placenames.
The Swedish names were written down by French clercs who could knew Latin.So Borgeby got to be Bourgquebu and Yvetot come from Ivetofta.
Caudebec is Kallebäck close to Gothenburg.
There are many many Old Norse words in English.
Grimsby, we, you, they, house, husbound, I think I could tell you about 150 and there probably are even more.
Things are more compilcated that your article tells.