Sorry, I may have misunderstood you. Are you saying that if the non throwing in team doesn't have a player in the hookers position (2 and 2) you don't worry about it?
Yes, you misunderstood, but I am to blame. I always ensure, early on, that there is a player in the hooker position, and I continue to watch for it throughout the game for the simple reason that there is time for it. That's what I was trying to say in the previous post.
However, because the dynamics of XVs vs 7s rugby are different, if the ball is thrown "fast" at the lineout, I won't be getting out the tape-measure in XVs, as long as there is a hooker in the 2 and 2 vicinity in XVs - an immediate FK for 19.8 (j) would be harsh in XVs since it can be so easily managed.
In Sevens, on the contrary, not committing a third forward to the LO area potentially means an extra 'back line' defender which eliminates attacking options, although of course their receiver can choose not to be in his (or her) spot.
I "don't worry about it" because I have the time to "manage it", and I would worry about "dancers" if only for the fact that by early management I let both teams know I'm watching something easy to watch, so I've not had any "dancers" yet.