Pretty sure most people in Revenue, government and anyone with any passing interest, professionally or otherwise, in multinaitonals would have been well aware of Apple’s (and others) tax approach long before 2012. The loophole doesn’t stop Apple from being taxed 12.5% on sales actually made in Ireland. It is profit earned elsewhere that is not taxed
That loophole has now been closed by FG since 2015. It would not have made a blind bit of difference retroactively in 2012 or 2013 as laws don’t work backwards.