This premise needs balance.
Williamson averages 38.25 at a strike rate of 69 from six innings against Australia, compared to an overall average of 46.71 at a strike rate of 84 in 92 ODI innings. However, that includes key moments, notably lofting himself into cricketing folklore against their transtasman rivals on February 28, 2015 at Eden Park.
With New Zealand nine down chasing 152 for victory, he deposited a match-winning six off Pat Cummins over long on to finish on 45 not out.
"I was looking to hit a boundary, ideally a six, because it was quite tough the way [Mitchell] Starc swung the ball throughout the innings," Williamson explained afterwards.
"I tried to keep the total out of my mind and just bat. It doesn't matter how you do it, as long as you do."
The Australians were cunning, too. Captain Michael Clarke made fielding adjustments within earshot of Williamson to pique his interest, but few can get inside the New Zealand No3's batting mind.
The best to make such a case was Indian off spinner Ravichandran Ashwin during the recent test series. He dismissed Williamson four times in as many innings. Ashwin recognised the New Zealand No3's desire to use the depth of the crease and kept tempting him to cut off the back foot. Ashwin picked up two bowleds and two lbws but also got the ball to spin, which mightn't be the case in the upcoming one-dayers.
Australia have preferred a frustration strategy in the past, bowling on a good length outside off stump. The idea was to reduce Williamson's ability to whip the ball off his pads and to encourage him to drive on the up into the covers.
One of those dismissals, at Wellington on Waitangi Day, was secured by debutant leg spinner Adam Zampa. Zampa will be tasked with doing the same this week, but might need to brush up on his googly or flipper. Anything going away from the right-handed Williamson tends to get milked for runs, especially if it's short.
Expect Williamson to be revelling at the prospect of leading his team into the cauldrons of Sydney, Canberra and Melbourne.
Last summer he impressed local scribes who, when he made one of New Zealand's finest test centuries at Brisbane, spread a rumour he might have been born in a manger.
Captain Brendon McCullum described it as "probably the best hundred I've seen from a New Zealander in the time I've been playing" and even grizzled Channel Nine commentary veteran Ian Chappell anointed Williamson's pedigree.
The telling part came at stumps on the second day with Williamson 55 not out. He didn't remove his helmet before the boundary rope, a nod to refusing to accept the job was anywhere near done as he strove to tame Australia's bowling into submission through subtlety rather than savagery. It's hard to imagine circumstances changing next week.