I've heard of but never seen this approach actually used to prevent a dog from worrying. However, I'm with Twizzel on this, especially with a 6 mnth old pup. I wouldn't put any pup in a confined area with even my Soay ewes. Think they could seriously injure a pup, or pup might 'turn on' the sheep, or pup will lose trust in you, or lose confidence in general or many other negative scenarios. Not sure that you would be able to manage or control the situation effectively enough to achieve what you are hoping for.
At 6 mnths pup is still very young and immature and in general their obedience level is not high or consistent at that age. Think I would concentrate on that and use a long line when in with sheep.
I can well understand your need to prevent chasing/worrying. There are others on here that will probably be able to help you with that ..... my retrievers don't tend to have the drive/desire to chase so not had to deal with that problem very much whereas your lurcher is probably wired to be 'keen'. Think Plums and her dog completed some lessons on this .... maybe she will be around soon.
Good luck with it.