Knitting on Sweatshirt

I just cme across a sweatshirt whose neckline had been cut off about halfwayu between the neck and the shoulder seam. somehow that portion had been replace with knitting, sort like a Fair Isle sweater. Has anyone ever seen these and know how to do this? I can’ t figure how to start the knitting. :shrug: :?? :shrug:

I’ve seen knitting or crochet added to fabric before. Although, I haven’t seen it done with fair isle.

and there is a video on YouTube showing how to attach crochet.