Both routes have exact same 21-day advance, roundtrip booking required, fares for same $236.80/$306.80 price (VFVQA0BQ/VFVQA0ML). Looking at Google Flights, it just seems they are somewhat stingier about releasing availability in V and other lower class buckets on MSP-SJC flights vs. MSP-SFO flights (but you can certainly find availability on both flights on less popular travel days and bookings further out). So it's less about the actual fare filings, and more about what buckets are made available on flights. For MSP-SJC, you have to search into April before you can find availability in both directions in V bucket.