Even if I-305 was extended recently, I would think that it would be concurrent with all of I-80BL north of US 50 instead of part of it.
Problem is that I-80BL north of where we have I-305 ending doesn't meet Interstate standards. That's a major reason why the I-80 mainline was relocated north of Sacramento, from what is now I-80BL and US 50 to what used to be I-880.
The
AARoads guide for I-305 indicates that I-305 once ended north of US 50, but was later truncated to US 50. This may have happened after CHM's Interstate route files were drafted, and I-305 was never updated.
I'll poke around some more before truncating I-305.