It did, sorta.
I carefully unravelled the picked up sts joining the sleeves to the body of the shrug, and it worked fine. I wasn't happy, however, with my reverse engineered cast-off. And perhaps more to the point, I wasn't happy with the decrease I'd done.
In modifying the pattern, I'd had to turn what had been an increase round to get k2 p2 ribbing to turn into k3 p3 into a decrease round to turn k3 p3 ribbing into k2 p2. I wanted a centred, non-slanting decrease. I made something up, a kind of fudged m1-centered 2 st decrease hybrid monster.
After some consideration, I ripped the two sleeves back and started again. Probably unnecessary, but hey, if I wasn't going to be happy with it, I wouldn't have worn it... The good news is that it's a quick knit, only 10 inches of ribbing in all for each sleeve. What's taking longer is the k3 p3 ribbing on the 400+ sts of the edging. SLOOOOOOOOOW....