Portugal is one of the top 6-8 teams at the World Cup by any quantifiable or objective measure. That means a quarterfinal finish for them would ordinarily be what you would expect from them. But teams that surprise or disappoint are those that do better or worse than what you would ordinarily expect. In Portugal's case, they would surprise if they finish beyond the quarterfinals and, in particular, if they make the final (not to mention if they win the tournament). They would disappoint if they fail to make it out of their group or if they get knocked out in the R-16. On the other hand, to pick the AFC teams to disappoint means picking them to do worse than they would ordinarily be expected to finish. Given that all of the AFC teams (except Iran) were in the bottom pot and none are favored to advance from their group, I am not sure what it means to say that the AFC teams will "disappoint"? Sure: if they go pointless and get thrashed, that would mean they have done worse than what would be expected. Otherwise, if even one of them manage to advance from their group, or if more than one of them finish 3rd instead of 4th in their group, that still means they have done better than their rating and billing.