Thanks for starting this, hope to learn a bit.
I don't want to touch the lineout stuff, but from watching recent games (with the associated commentary) I have been wondering about this very topic! How did you know??
What I don't get is this 'insistence' on which number on the back does what. It may be purely coincidental? I mean why is that the number 6 has to be the wide runner and number 7 in tight, and number 8 the hard hitter up the middle. It is that sort of thing which I don't understand.
If those roles are required on the field, then would it not be sufficient that someone fills the role? Why is it that the number 7 can't be the seagull and vice versa. (if I got these numbers back to front at any stage bear with me m'k? Tis the concept I'm asking about)
Maybe it is because of which side of the scrum they pack??
I would have simply thunk it was a case of 'get the best guy on the field', in other words 'so what if there are two number 7's (or whatever)..if the second number 7 is 'better' than the usual 6, just put him in that position cause that part of the scrum has to pack, and let him rip'.
Let's say Pocock was not injured, and smith was available. Assuming pocock is the 'best' along with smith, why would you not play both?? (hearks back to your balance bit and I'm assuming that these two compete for the same spot)
Really looking forward to getting some insight on this, thanks ever so much for bringing it up.
(hope you understand my misunderstanding so the responses will help explain)