California Penal Code Section 289:
(d) Any person who commits an act of sexual penetration, and the victim is at the time unconscious of the nature of the act and this is known to the person committing the act or causing the act to be committed,
shall be punished by imprisonment in the state prison for three, six, or eight years. As used in this subdivision, “unconscious of the nature of the act” means incapable of resisting because the victim meets one of the following conditions:
(1) Was unconscious or asleep.
(e) Any person who commits an act of sexual penetration when the victim is prevented from resisting by any intoxicating or anesthetic substance, or any controlled substance, and this condition was known, or reasonably should have been known by the accused,
shall be punished by imprisonment in the state prison for a period of three, six, or eight years.
Turner was convicted of one count under 289(d)(1) and one count under 289(f). Those 3, 6, or 8 year terms were on the books when Turner committed his crimes and was sentenced; they were not added by the legislature in response to Turner's sentence.
Title 4 of the California Rules of Court, where the sentencing "guidelines" are found, are actually vague in laying out how they should be applied. The judge in Turner's case exercised a great deal of discretion in coming to the sentence that he did; that outcome was not compelled or even driven in any way, shape, or form by some imperative found in the felony sentencing rules. The prosecution applied those very same rules and asked for 6 years imprisonment.
Here's their sentencing memorandum.