I'm curious about how you 'harvest' a section of tube without it unraveling.
Maybe cut it around, remove the little bits of yarn, then unravel a ways on purpose, and knit the unraveled yarn through the edge like a normal bind-off?
Circular knitting typically uses a technique called "grafting" or "Kitchener stitch" to close tubes seamlessly without unraveling - you'd temporarily secure stitches on holders, cut one strand, then use a tapestry needle to mimic the path of the yarn through the live stitches.
They might be sergering the edges.
Thread a flexible needle (usually called "circular") or a wire through a full row near the cut, unravel the remaining rows, then take a fine crochet hook to chain the loops together.
Or just hem it, but that doesn't look like what she does.