If you press each row a different direction, it helps to nest the seams and you get flatter seams that way and it can also help with lining up your matching interesections.
However, when you have multiple seams coming together in one spot, it helps to have them circle around in the block, and to press open the two halves, putting half of the bulk on both sides. (Kaleidoscopes, NYB, some other PP blocks, etc)
After I make a couple of blocks, I look at the backs and decide if they are too bulky and what I can do pressing to remove some of it.
Each project is different and all of us approach this subject differently :D:D:D