They say to quilt the same in both directions
The fibers in the insulation run in one direction
If you pull along the fibers, it resists pulling, but if you pull sideways, it pulls apart
Therefore, quilting across the fibers will accomplish something, but quilting parallel to the fibers doesn't accomplish much
I think their recommendation to quilt the same in both directions is overly conservative, it's like they say that so that if someone quilts in the wrong direction they won't complain.
If they're conservative about that, maybe they're conservative about the quilting distance also.
Examining the Apex and Primaloft, they seem very similar
I just made a sleeping bag with 3 oz Primaloft, I quilted 48 inches apart across the fibers, and 72 inches apart parallel to the fibers.
I wonder if I'll regret that : )