You’d think it’s the language spoken in England

The sort of English you’ll see in literature, newspapers, any remotely formal communication, in grammars (which learning materials are based on as well). The stuff learners will aim to learn.

Differences between US and UK English, and the dialectal variety within each of them, are not all that relevant here. Where I live, students are taught British English, but no professor ever chastised us for using American pronunciation or vocabulary. Both are within the range of what natives will find acceptable.

but the rest is perfectly cromulent

“Competences”, “planification”, “to hop over” (=to refrain from)? Sorry, that stuff is downright grotesque.

Remember these aren’t high school mistakes they’re stuff that C2 speakers use

I can’t remember that because the WP article didn’t claim that. In fact, if you make these mistakes, you’re not C2, by definition.

just as you’ll see American generals writing reports using “less” instead of “fewer”, or “good” instead of “well”, or “who” instead of “whom” (shudder). “was” instead of “were”.

Except that this is language change from within the native community, in their native language, aimed from native speakers at other natives who will understand or (if they don’t understand them or use a different variety) correct them. Some of that stuff (who-whom, was-were) is well-established in already existing usage and dialects, it’s not an innovation at all.

That’s language evolution, plain and simple, things change as they always have and the language does different things in different places.

I’ll repeat myself: no, this isn’t ordinary language change, as this “Euro English” is simply a local characteristic of this or that speaker who failed to learn English as it is used by native speakers. ‘Euro English’ is not a real unit, as it has no defining characteristics. Imagine a European using some calque from his native language while talking to a European who has a different native language and who can’t understand the calque - this is not what happens in a normal speech community, these people will fail to understand each other, and their English is not a stable or reliably identifiable linguistic variety. You can see that especially in the table with “Euro English vocabulary”, where words are clearly marked by their origin, and they won’t be understood or will be found absurd by many other Europeans.