Re Sean Twomey, I would say that his league performance against Galway was not as impressive as some other posters thought - he scored two goals but iirc didn't win much possession. He was also a bit unlucky that UL's run in the Fitzgibbon and his subsequent injury meant he didn't feature in any other league matches. So I agree that to a large extent he is an unknown quantity at senior intercounty level.
That said, he was consistently picked on the 26, presumably as a half-forward option - and what he would bring to that line would primarily be a physical presence, hard work and hopefully a puck-out option. Given that, and given that Cork struggled for long periods in the last three matches in the half-forwards in all of these respects, I find it very odd that he was never tried. Of course it would be a gamble throwing him in, but apart from O'Mahony against Tipp and Clare Cork had no other player on the bench who would potentially be as good in those specific respects.