This blanket is basically stockinette stitch. When I pick up stitches along a st st vertical edge I usually pick up 1 in each stitch for 3 stitches and then skip one. Repeat that sequence. Possibly because the gauge is quite big they are skipping more stitches. But I just want to point out that the number you pick up really doesn't matter. Well, it matters in that if it is too many it will ruffle up and if not enough it will pull in, but the number doesn't matter, the result does. You can try picking up every other stitch and seeing if that looks good (they give an odd number, but even that is not 100% necessary as long as you work knits over purls and purls over knits so that you get seed stitch) and fudge at the end to get the odd number if you need to (and want to). If it doesn't look good you might try to pick up in each of 2 and skip one or even 1, 2, 3, skip and see what happens. (It is easy to rip out and redo until you get a good result) I never worry about picking up the number they say to anymore, but just what seems best. Of course, you want to do it the same way on each side within a stitch or two.