"I don't think by any means it's been a great start," he says from Bangalore while preparing for today's second test against India.
"It's gone amazingly fast. The learning curves in the last two years have been huge."
That's exactly what prodigious talents before him have found, and precisely what the new Next Big Thing will soon discover. Test cricket is difficult. Not many kids can swap first-class cricket for the highest echelon without some stumbles along the way.
"The game can be very hard for different reasons. It might not be facing the fastest bowler in the world or the biggest spinner, sometimes it's the pressures that come with playing international cricket that aren't even part of the game."
An obvious example of that pressure was the fervour with which Williamson's arrival to international cricket was greeted. After a stand-out under-19 World Cup in 2008 and an even better domestic season for Northern Districts, the country had found the next Martin Crowe - another who struggled with his first taste of the top.
For a teenager, it was quite a tag. But Williamson denies reading too much of his own press, insisting the hoopla has failed to affect him.
"My first two one-day games, I got two ducks, so you soon forget about any of that.
"Cricket's a real leveller so all that sort of stuff is just peripheral. It's irrelevant to me. You're judged by the way you perform - you score runs or you don't score runs. It's pretty black and white."
Williamson has managed to score plenty of runs - including two centuries and five 50s, most recently in the first test in Hyderabad - but he wants more. Most 22-year-olds would probably be content averaging 32.84 in test cricket, but not Williamson.
"It's not something I'm overly proud of," he says of his average. "But it is evidence of lessons learned along the way and the failures and successes.
"That's absolutely something I want to improve and I guess that comes back to my drive in playing the game."
That drive also leaves Williamson adamant in his desire to play all three forms. Some would prefer to see him knuckle down in the white clothing and forget the more frivolous pursuits, while others believe New Zealand's best batsman should help the side in any way he can. (There's also the small matter of the majority of the sport's earning potential being tied up in Twenty20.)
Williamson positions himself firmly in the multiple-formats category.
"I enjoy the challenges of adapting to different formats. That's something I've always done and it's something I want to continue doing."
Williamson also showed his wares as a future captain when he became the youngest man to lead the side during last month's Caribbean tour. But with the team in capable hands, he's not about to stage a leadership coup.
"I'm not even conscious or thinking about that. It was a real privilege to get to do it while Ross [Taylor] was out with the injury and I enjoyed it, but it's not really something that's on my radar.
For Taylor's part, he sees a bright future.
"He thinks about his game a lot. He's always picking up other peoples' cricket bats and he loves asking questions to be a better player. I'm sure over the next couple of years you'll see a world class Kane Williamson arrive."
That's in the future; Williamson's radar is set to today's test and no further, even if just about everyone else prefers to prognosticate on what the future holds for such a precocious but unsatisfied young man.
KANE WILLIAMSON AFTER 15 TESTS
Age: 22
Aggregate: 854
Average: 32.85
Highest score: 131
50s/100s: 5/2
Ducks: 4
MARTIN CROWE AFTER 15 TESTS
Age: 22
Aggregate: 602
Average: 24.08
Highest score: 100
50s/ 100s: 1/ 1
Ducks: 4
Crowe ended his career with 5444 runs, 18 50s, 17 centuries and an average of 45.37.
