Earlier quoted context omitted.
This has another side: non-native speakers are expected to understand different accents and flavors of English just like an anglophone would. For example, as a Russian native speaker, I had real trouble comprehending even a slightest French accent, while having zero issues with others. I'd imagine there are a lot of ears "incompatible" with my own accent, so I spent a fair amount of time on getting rid of it.
Even accents from Britain itself can be weird. Ever spoken to a Scot, a Liverpudlian, or a Brummie? Even people who've spoken English daily for decades will do a double take if they're not used to it. If you listen carefully, the range of vowels is quite wide, for the same word in different accents. The probably throws off a lot of people.
I think this diversity, while large, is still less than in many other languages. As one example of many, just within Europe there are accents/dialects of German in Switzerland that are largely mutually unintelligible even to some other Swiss German speakers, and nearly entirely unintelligible to most Germans. This is also true for dialects of Italian, or even Dutch, according to friends from those countries. It's generally even more fragmented outside of European languages.
Unlike English, some of these cases don't even have easily standardized registers. In my experience, people in Birmingham or Glasgow, for instance, can fluidly switch to a more standardized accent and dialect that's natively or "intuitively" understandable to a speaker from North America or South Africa.