These aren't knit in the round. You'd use a provisional CO at one end, knit the length, then graft the ends together.
You can still do cables in the round, you can purl between the cable stitches, but they'd run from the bottom edge to the neck edge, not the long way. You'd have maybe 20 cable repeats side by side instead of one or two.
Garter stitch is a stitch pattern you get when you knit or purl all rows knitting flat; you can get garter stitch in the round by alternating a knit a purl row. But cables can be done in the round, you just knit the cable stitches and purl the stitches in between them.
sue- knitting heretic