This option can not (should not) depend on the update statistics XVM. What about the players that do not use XVM? XVM should read the nationality (language) of the player's settings on the website WOT or language game client.
I have updated data XVM, I set your language, but it still shows me the EU flag.
Edit: 27.12.2014 g. 15:50
I updated my stats (3-4 time) and now I have correct flag. It is a pity that the correct flags have only players who use XVM (of course after the update statistics).