The California State Parks GIS Data seems to have "Authoritative" data according to their website. While it's freely available, it seems to be encumbered by a copyright.

The CPAD data seems to match the current OSM boundaries. The California State Parks GIS Data seems to more closely align with the existing roads.

According to the California State Parks GIS Data, Smith Grade is completely inside the park with no gap, and the park boundary next to Empire Grade generally seems to have a uniform gap from Empire Grade in this area.

Take that information as you see fit.

Here are some additional resources that may provide help for anyone interested in this topic around this area:
https://www.parks.ca.gov/?page_id=29682
https://csparks.maps.arcgis.com/home/item.html?id=0fea4fa1db734794bdb3b5410bb3eed9
https://csparks.maps.arcgis.com/apps/mapviewer/index.html?layers=0fea4fa1db734794bdb3b5410bb3eed9
https://www.calands.org/
https://www.mapcollaborator.org/cpad/?base=map&y=37.02805&x=-122.18067&z=12&layers=cpad_ownership%2Cnotes%2Cpolygons&opacs=50%2C100%2C25