I've always seen the profession/background bonus as the very minimum someone is likely to learn by practicing that trade, even if completely disinterested, whereas the "freebie" points represent a character's true passions and interests....your character might have been a farmer once (because his father was), but it's not certain he learned the trade well if he never really liked it.
A character keen on taking over Poppa's farm will sink his freebie points into the farming skills. A character who spends his day at the farm daydreaming about slaying dragons and rescuing princesses will still learn something about farming - that's the +10% background points in farming. But he spends all his free time sparring with the local guards - that's the +30% into Sword & Shield.
Regarding this, I actually think the percentage is spot on. Remember, this is a hypothetical 21 year-old with tremendous natural talent (good stats), coming from a warrior culture and trained non-stop from a young age. It's the +30% freebie points in particular that represent relentless training and practice. For all intents and purposes he is a Spartan.Good stats get you 30+, plus 10 for background plus 10 for profession plus 30 for free points and we're looking at 80+. Keep in mind this is still a character below 21 years of age. I know some cultures will produce an absolute badass by 21, but not everyone is a Cimmerian, Spartan or Cheyenne.