This doesn’t keep Californians from traveling to those states and it doesn’t keep people from those states from traveling to California. Implying that this is a “travel ban” in the same sense as Trump’s is wildly misleading.
Officials from California are much more likely to visit other states within the US than to visit foreign states and so the cost/benefit calculation is different. The only people from California even remotely likely to visit foreign countries on the public dime, much less countries that have poor human rights records, are the governor and his aides and implementing a ban on use of public funds for such infrequent trips by such a small number of people would be counter-productive.
California sanctioning US states instead of foreign countries is also partly because the governments of those states can reasonably be expected to know better. Holding people that you know to account is more reasonable and more necessary than holding strangers to account.