That's a weird system (as everything in Spanish football
From my understanding, from the 1st stage, we don't really care at which position we might end (assuming obviously that we will be top-3).
It's better finishing 3rd with 38pts, than finishing 1st with 34pts for example
But the second stage is a little bit strange, because there are only 6 match days, thus it won't contribute much to the points tally, so the first stage seems more important (usually, the latter stages are more important).
So if let's say, we can have the luxury of taking the 1st stage by storm, getting the max of points finishing 1st with a good difference from the others, we can relax on the second stage, and use a 1-month period for getting prepared for the knock-out stages.