"It's well within the rules," said Kidwell. "We hadn't made a decision on who is going to fill that position so that is the reasoning behind it."
But it's a highly unusual situation that the players, and especially the captain, don't know.
Bromwich may well be foxing but the entire situation indicates some indecisiveness on the part of Kiwis coaching staff.
It's meant that the decision has become a key focus for media and fans, and many of the questions on Saturday were centred on that topic.
When asked what his basis for the No6 decision was, Kidwell stuck to the clichés.
"[It's based on] what's best for the team and what's best for the game plan," said. "You'll know an hour before the game."
Kidwell added that the move to leave out Jason Nightingale and Jared-Waerea Hargreaves were "really tough decisions but the right ones for the team".
Leaving out Nightingale is a brave call, especially given David Fusitua's inexperience at this level. But it's also a positive move, as Fusitua brings more attacking threat than the Dragons winger.
However, Fusitua and centre Solomone Kata have never played together as a combination on the left edge, and their defensive communication will be key on Monday.
The Kiwis completed a brief captains run at Anfield on Saturday, with many of the players awestruck by the surroundings, as they posed for photos before and after the session.
The dimensions of the field - which have been shortened by 91m for safety reasons - means the respective kicking games will be vitally important, which is where the Kangaroos would surely have the edge. Indeed, the sight of Cooper Cronk and Cameron Smith reeling off numerous 40-20 kicks at the end of training was an ominous sign for the Kiwis.
"We have one goal in mind," said Kidwell. "Our attitude has been exceptional this week and it needs to be. Come [Monday] there is no more time to improve...it's time to win."
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