variations on GMT-8:00

Hi, this is just historical curiosity. I notice that "Rule CA" is applied to Zone America/Los_Angeles (and therefore US/Pacific and US/Pacific-New). But Zone PST8PDT does not have these same (California?) rules. Is there a political precedence for this? I see the bulk of the differences are the period from 1948 until the Uniform Time Act. But it's also curious that America/Los_Angeles references the US rule that defines PST from 1983 to 1918; whereas PST8PDT does not. Why this discrepancy between PST8PDT and the equivalent geographically named zones that use PST? If there is an online explanation for this kind of thing, I'd happily go RTFW. ../C