It seems that the Purl 1 is supposed to be from the farthest left of the 3, then Knit the 2 on the right (first) cable needle...
If all stitches were on the same needle, it would be a little difficult getting at the far left stitch without extra twisting, as 2 other stitches would be in front of it on the other side.
I might have to try it to see if it's possible though!
You could always slip all 3 stitches onto the same needle (provided it's double-pointed), then after holding those to the back and knitting 2 from the left needle, slip the farthest left stitch back to your original left needle and purl it. Then, knit two from the cable (or DPS).
If that makes sense... (and provided I'm understanding the pattern correctly)