Does it mean changing political boundaries to favor one party or class over another ? Why, yes, yes it does and that's what happened in California.
The last time Orange County was redistricted was 2012, it was done by the Citizens Redistricting Commission made up of 5 Democrats, 5 Republicans, and 4 from neither major party, and requires a supermajority of votes to pass a change to a district, and after the change it went Republican.
The Republicans lost Orange County because the Republican majority there was based on votes from culturally conservative Asian-American, Middle Eastern, and Latino groups. All of which the Republican party has alienated with their decidedly racist attitudes since Trump took office. Just look at who Orange County Republicans were sending to Congress. It was not the normal middle aged white dudes of the Republicans. The conservative people that Orange County voted for in previous elections do not feel welcome in the current Republican party.
It is the Party that changed, not Orange County.