Simon : The bill does not mention "15-17 year olds", it says "minor" and "within 10 years", so would be applicable to an 18 year old and an 8 year old child.
Crimes of sexual conduct with a minor under the age of 14 are prosecuted under the Penal Code § 288 as a “lewd and lascivious act with a minor.” Sex offender registration is mandatory even if the conduct was "consensual".
So this Bill does not apply to any child victim under the age of 14.
At the moment sex offender registration is also mandatory for crimes of sexual conduct other than sexual intercourse (sodomy, oral copulation or sexual penetration) with a minor 14 years or older, even if the conduct was consensual and the minor was within ten years of the offender.
However, If the minor is 14 years or older and there is consensual sexual intercourse with an adult (older than 17) then the prosecution is for unlawful sexual intercourse under Penal Code § 261.5 and sex offender registration is not mandatory if the minor is within ten years of the offender. but it remains for the judge to evaluate.
The purpose of the Bill in question is to treat those who have some sort of consensual sex (other than intercourse) with a minor, 14 years or older, in the same way as those who have intercourse with a minor are treated, as far as sex offender registration is concerned. Nothing more nor less.
Please note I should have qualified minors affected by this Bill as 14 to 17-years-old, rather than 15 to 17. I had in mind it was older than 14 but it is 14 and older.