Ok, so let me elaborate on that for a while.
I consider British English as a stem and any other variation of it, like american, australian… as offsprings.
I don’t claim they are wrong, I simply say that British English is a matrix of the language. Like everything that lives (and languages live their own life, don’t they??) it evolves but the stem: grammar principles, vocabulary and stuff, stays unchanged for a longer period of time.
English like any other language is very susceptible to changes for it’s worldwide. But still - the stem stays British and this is considered as proper english, not only by me but also by experts who deal with examining ppl all over the world.
In the USA ppl don’t ‘feel’ the difference between, for instance ‘where have you been’ and ‘where were you’. I was asking them about it and they told me: hmmmm there is almost none difference you may use them interchangeably.
Of course ppl i asked weren’t experts but they were native speakers so they knew best. Right?
As we all know, in tests checking our knowledge of English there is a lot of questions dealing with the difference between past simple and present perfect. I’m sure that a lot of Americans would make mistakes in those tests, being at the same time native speakers.
That’s why i claim that British English may be considered as ‘perfect english’
On the other hand i’m fully aware that there is a lot of varieties of “British English”
I hope you get my point