California isn't "very left-wing". It's liberal, centre-left if you're being kind. The democrats are a centre-right party with some mildly-leftist pockets of members.
By US standards, California is very left-wing. International standards are not super relevant. (I'm also a bit skeptical of the cliche that the Democrats are a right-wing party internationally. For example, Obama endorsed Trudeau in Canada. But again, not super relevant.)
Democrats were also just a big tent party for a long time, with more 'real right wing' members than 'real left wing' members, maybe that's the reason for the platitude.