Yeah I genuinely disagree with this and feel in ODIs he was already really, really good and treated as such by opposition bowlers. I feel his 1998 was one of the best years he ever had as an ODI batsman - by '99 he was definitely close to his max potential in the format even if he did go on to have his best year a while later in arguably 2003 or 2007(depending on how much you rate his 140* in the '03 final)
peaks are tricky. Here's a great run he had from late '97 to early '99,
https://stats.espncricinfo.com/ci/e...an;template=results;type=batting;view=innings
averaging 55 over 32 games, especially around that era and for a number 3 is pretty special. In a 32 game period he would have only ever averaged that high again around 06-07, and of course ODI batting had changed a lot by that era.
In '99 he was a long way from his best ever year/performance in terms of time, but he wasn't that far off in terms of ability
He even managed to to reach 4th in the world in early '99!
ICC Player Rankings