That's because "Breeder" is
a constant for every horse, and is stored in the database. "5th Previous Owner" is not a
constant for every horse, and is not store in the database.
Plus, consider the following:
5 stables (A-E) own 1 horse throughout its life.
Stable A breeds the horse, sells it when
it's 6mos old to Stable B.
Stable B owns the horse until he's 2 1/2, then quits the game
and the horse reverts to FF.
Stable C joins and gets the horse as a starting horse, keeps
him until he's 4.
Stable D buys the horse at auction before quitting, and the horse reverts
to FF again.
Stable E gets the horse as a starting horse.
If we go with "FF is the
default owner", then it would appear that the horse was owned by FF from 6mos-2 1/2, and age
4 to when Stable E joins. Given how FF races its horses (with no rhyme or reason

), it
would appear that FF owned him for 95% of his racing career, which would be a
misrepresentation of his racing ability (making him appear better if he had a
not-so-successful racing career, or worse if he had a successful career).