Hi,
I am still waiting for the phone (most likely for a few more weeks).
I have added your link to the Guardian article to the list of curated articles.
Right now I do not remember another article mentioning this problem.
But that’s because most did not test it, according to my memory. Most of the articles are just mere news-flashs reporting just the specs.
Of course I have not read all of them and not just becaus many of the languages I do not understand. 
You might try to look, if you find some more reference to bluetooth performance.