hi there ,
I don't mean to patronize but as an ESL you shouldn't be fussy about such things ! It may become important just when your'e speaking to a native speaker , even if that's the case , talking from experience , as long as what you say is understandable nobody pays that much attention to those small details . you even might see Americans use some of brit terms according to dictionaries and when u ask them, they don't even know it's something british .and if your'e going to live in an English country , you'll learn their terms gradually as u're surrounded by native speakers .
besides both have taken influence from one another and maybe british English has done more . so you get to see brits use Amercian slangs and sometimes even accent , like they might say addidute instead of attitude
However I'm aware of the fact that this article is reserved for more formal and learned English and not and the vernacular but hope you don't mind if I digress a little bit and point out another difference worth saying , which is how Amercians change the letter 't' to 'd' when it's placed between two vowels , like later , pronounced as lader or water turns into wader , albeit there are some exceptions to this
there was something about dropping the consonant 'h' in brit English in the article . well in fact Amercians do the very same thing in spoken English when it's linked to other words like you say isi instead of is he , or withim rather than with him .
all in all the article was thorough and It wasn't my intent to belittle it and thanks a lot to the author and all the effort he's put in . I merely wanted to speak my mind
God bless you all , bubye