Nah in the scenario I outlined the records going into the final week would be:
Niners - 11-5 (losing one of their next two)
Seahawks - 13-3
Rams - 12-4
A Niners win in this scenario gets us the division (assuming a win against the Cardinals at home) - but if you're the Niners, as you can see, a win for them does next to nothing. They can't catch Seattle if it plays out like this.
So the question then becomes, do the Niners care which wildcard seed they are? The difference between 7 and 6, I would argue, is negligible. You're either going to Philly, Green Bay or Chicago. All cold weather cities, all flawed teams - AND, you probably have no idea which one anyways, until kickoff.
The ONLY caveat in all this is, the 5 seed is clearly better - and IF the Cardinals were to beat us, and the Niners beat Seattle, they would be the 5 seed.
So the question is this:
If you're Shanahan and have the most injury prone team in the history of the NFL, do you play your starters in the off chance that the Cardinals can go into LA and win?
My answer to that would be hell no.