I don't believe that "serger" foot actually cuts fabric; at least the one I had years ago did not. It simply guides the fabric edge so the machine can do a zigzag stitch enclosing the cut edges. A serger uses 3 threads, so the stitch itself is not at all like a serging stitch; just a zigzag type stitch. Most sergers these days have differential feed (controlled feeding of the top fabric along with the bottom fabric) which makes it easy to finish the edges of knit fabrics without stretching; a sewing machine, even with a walking foot, does not have differential feed so knits tend to stretch and distort.
There are a few sewists who actually use the "serger" foot, but most do not find it useful. It is definitely not a substitute for all the things a real serger can do.