In the round?

Since I’ve learned to knit in the round I much prefer doing sleeves and the like in the round so I don’t have to sew a seem later. So the first pattern is a girl’s sweater that I’m wondering if there’s any reason not to do the sleeves in the round?

The second is a baby blanket that has a mock crochet border. She goes all the way around the blanket but instead of connecting, she does rows instead and sews the two unconnected corners. I’m also wondering if there’s any reason I shouldn’t do it in the round?

I believe the only reason you’re supposed to work the sleeves flat is because of the lace pattern.

Row 1: K2, * yo, ssk, k2; repeat from * across.
Row 2: P2, * yo, p2tog, p2; repeat from * across.

You’d work row 1 as written, but row 2 would have to be reversed.
I [I]think[/I] (I’d have to try to be sure) that p2tog would reverse to k2tog tbl. So, assuming that’s correct, Row 2 would be worked

k2, *yo, k2togtbl, k2

Try it and see if it looks the same as the body.