I mostly agree. In my many years of playing and GMing, I've never had the case where two players wanted to play the exact same "archetype". So the hypothetical situation of (for example) the human archer player complaining that the elf archer player is unfarily advantaged just never happens. Never. In the vast, vast majority of groups I've GM'd, the wizard, warrior, thief or other is perfectly happy to have a kick butt elven archer or halfling slinger along. That extra +10 doesn't hurt them, it hurts the bad guys.
My experience is, players complain when various classes or archetypes are unbalanced in a way that one 'archetype' makes another superfluous. So, just making up a fake example, if the thief's abilities make them a better archer than the archer, that's when the archer player complains. That's why magic-users are often the focus of "OMG it's OP'd" debates - because they often gain abilities that make them better at core abilities that other archetypes are supposed to personify. Would your thief rather have high stealth and climbing skills...or be able to fly in, invisible? Many games don't balance wizard-types well. But that's something of an aside.
In any event, I don't really see the issue of elf attributes in WFRP4 as a major one that's actually going to crop up in games. Having said that, if a group wants to drop some of those +10s for balance, I don't think that's going to really impact the game much either.