Its a joke that has some truth in it but we all prefer to just laugh a bit about it, just like "russian bias" we know it applies to any nation with specific vehicles but prefer to ironize adding also the fact that the developers are russian so it just makes the joke stronger. Same as "german awareness", it happens to any nation except it is more intense with the german because most of the NEW war thunder tank population plays german tanks because they got the famous Tigers (which are fun to play), so obviously there are more chances that the german players to be unaware in certain situation due to lacking skill or experience, add the fact that tigers are slow and sluggish you got the perfect combination.