didds
Resident Club Coach
If they advance or continue sideways until the ball leaves the lineout (and if advancing only the ball has to leave the LoT as no maul has formed) then we're in general play and defenders can cross the LoT and try to tackle ant any angle. Then you'd have obstruction from the players bound on the side or back.
So the team in possession were smart enough to keep it as a lineout but when stalemate happened they didn't have a plan B.
Gotcha Chris - that was the bit I was missing

Though whether they could claim obstruction by attempting to reach the ball "from the back" may be a moot point... we wouldn't expect a ref to penalise a supporting runner whose normal support running position prevented a chasing defender from reaching a running ball carrier after all.
didds