Not a fan, sorry.
The clip is teaching the dog to be erratic on the lead, it’s way too young to recognise “tension” and wearing a collar so there isn’t really any tension.
Far better getting a lesson with a gundog trainer, who’s first comment will be to teach your cocker to walk to heel, last! Get the basics in first - sit, stop and recall. Get a slip lead and learn how to position it correctly and use it properly, without causing any harm to the dog.
The other thing I wasn’t keen on was how tall the chap is compared to his dog and how he was leaning over the pup. If you really want to follow his advice then at least sit on the ground with your pup and don’t dominate it, otherwise you risk having a pup that won’t recall all the way back to you and runs rings round you when they do come back…..
I did like the way he was with the pup otherwise