Does propensity evidence in a sexual assault case have to be excluded from the criminal record?

In People v. Lopez, supra, 156 Cal.App.4th 1291, the defendant was charged and convicted of assault and rape of his half-sister. At trial the prosecution introduced evidence of an uncharged prior sexual offense he committed involving his cousin as propensity evidence. (Evid. Code, 1108.) The testimony of two witnesses showed the defendant had committed assault with the intent to commit rape against his cousin. But, as a result of a plea bargain in that case, he was only convicted of false imprisonment. On appeal the defendant contended that because he was convicted of false imprisonment based on a plea bargain, the evidence of the incident involving his cousin should have been excluded because false imprisonment was not a sex offense crime.