I'd almost agree with this. I'd say that the quality is only the starting point. I'd guess the engine takes quality and applies factors to make an actual performance figure for any given situation. I also think the wide range of these can swallow up any other factors.
But yes, a crap team that effectively counters Barcelona can win and do. Average teams can and do win muti-match tournaments too if they stick to a game plan which others don't cope with.
Its a nice comeback and a good story and the changes made may have had an impact. But its not compelling evidence.