The author praises Prop 103 and the protection it offers against higher rates, saying that Prop 33 is an effort to reverse those protection and allow higher rates for drivers who switch insurance carriers. He says that under Prop 103 length of time with current carrier cannot be used in determining the premium rate charged.
But it's a significant change in the law, which currently allows auto insurers to offer such discounts only to customers who have maintained unbroken coverage with their current carrier, not with others. The difference means, in effect, that insurers would be able to charge higher rates for new customers without prior insurance; that's explicitly barred by the 1988 insurance reform measure Proposition 103
But then he describes Proposition 103:
Proposition 103 barred the basing of auto rates on anything other than a driver's safety record, years of driving experience and miles driven annually. It allowed other factors that could be shown to have a substantial relationship to the risk of loss, including a driver's longevity with his or her current carrier.
So by the author's own statements Prop 103, and current california law, does actually allow the longevity with current provider to be a factor in deciding the premium rate charged and Prop 33 would seek to ban that permission and base it only on the continuity of insurance coverage itself, regardless of carrrier.
The new insurance carrier
could charge a higher rate if they wanted to, but why on Earth would they do so? They aren't going to pirate much business from other insurers by charging higher rates.