Are we suppose to agree with every thing a dictionary says?
If I pick up a bass that is marketed as perfectly balanced that's what I want.
Yes if you want to describe something a certain way then one main point is to agree on what that word means. I choose to use a dictionary but in order to have a conversation we all have to agree with what makes a flaw. I would take dictionary defintion as a reliable way to start.
Either way if the bass is marketed by the company as perfectly balancing and it doesn't then I would say it is flawed as it does not meet the companies defintion of perfection.
But if we hold a bass differently and it balances well for me and not for you I don't think we can say the bass is flawed.