The girl was going to tell the police that she wasn't RAPED. The police didn't say "it didn't matter, you're under 18". No, the police told her that she could get prison time for lying, which is when the girl decided not to change her story after all.
To ME, this seems more like RAPE (PC 261) than Unlawful sexual intercourse (PC 261.5). In fact, PC 264(c)(2) states: "(2) Any person who commits rape in violation of paragraph (2) of subdivision (a) of Section 261 upon a minor who is 14 years of age or older shall be punished by imprisonment in the state prison for 7, 9, or 11 years", which would seem to fit the 7 year sentence that the guy received.
Without knowing what the guy was actually convicted of, this is, of course, all conjecture.
He was convicted of rape. Not statuatory, but actual rape with forced oral copulation.
(Backstory- The mom walked in on her giving him a blow job and flipped out since they were a really catholic family. The girl was grounded and mom was going to make her transfer to catholic school. While she was grounded, my brother got a new girlfriend and the girls story changed. It wasn't until he was sentenced that she offered to tell the truth, but the DA scared her out of it. She said she was sorry, though- like that matters in the long run.)