Without knowing specifically which other threads you are referencing, its hard to say why that might have been the recommendation. Doing Crater Lake would make sense to do first, on a loop trip heading back to San Francisco, or possibly if the trip was being done in late fall where getting to Crater earlier would have some weather advantages.

In your case, it would pretty clearly make more sense to do Redwoods then Crater.

Going north to south does has some advantages, but its not that big of a deal, if other factors make it easier to head north, I wouldn't worry about it.