Which is correct and not much difference than them checking an offside decision in a build up to a disputed goal and not every offside decision in the game.
This is a debate that could go on for ever as how far do you go with technology? I think the system in Rugby is good in that a ref will ask the VT Official "Is there any reason I cannot award a try?" This should be applied to all goals and goal-line disputes and the Fourth Official could give an answer in less than 30 seconds...
