There has been a big push away from using 'trunk' based on the physical characteristic of the road, instead being used for "most important" routes - best interregional routes between large (city+ size) settlements. Primary is generally used for regionally important roads. Most of these major, interregional routes have been agreed upon for this state (see https://wiki.openstreetmap.org/wiki/California/2022_Highway_Classification_Guidelines) - though this list isn't set in stone, these state highways in the foothills are regionally important but don't serve any major interregional route (ie, say, Redding to Reno) so it would be a tough sell. But upgrading just this section because it is an expressway would be incorrect (see 'trunk' section of https://wiki.openstreetmap.org/wiki/United_States/2021_Highway_Classification_Guidance)

If you're concerned about expressway sections being visible, you might try the osm-americana style (https://zelonewolf.github.io/openstreetmap-americana/#map=10.06/37.8384/-120.606) which renders 'expressway=yes' sections with a double-casing as is more typical on US-style highway maps. I use this style to check that expressway tagging is correct at a glance.