- https://en.wikipedia.org/wiki/Alghero
- https://en.wikipedia.org/wiki/Andorra
- https://en.wikipedia.org/wiki/Balearic_Islands
- https://en.wikipedia.org/wiki/Pyr%C3%A9n%C3%A9es-Orientales
- https://en.wikipedia.org/wiki/Catalonia
- https://en.wikipedia.org/wiki/Valencian_Community
- https://en.wikipedia.org/wiki/Aragon
All of them share the coat of arms of the crown of Aragon: https://en.wikipedia.org/wiki/Coat_of_arms_of_the_Crown_of_A... . Thus using the "four red pallets on a gold background" represents all the speakers in different European countries.
That's why I say that I personally (as a Mallorcan) would much prefer the language to be associated with a Spanish flag than a Catalan flag. Some people would agree and some would disagree – ultimately the best thing is to not link flags to languages anyway.
To give you another example from Issen, they're also using the American flag for English which is probably even more controversial :)