Not necessarily disagreeing with the sentiment that improving after 27 is more unusual than the norm but the 2 in history intuitively seems low.
Looking at the current team over the past few years - Tavares had his career year in goals and points as a 28 year old. One of his team mates the past 2 years is Mark Giordano who set his career high in points en route to his only Norris trophy at age 34 with Calgary prior to coming to Toronto. Another team mate of theirs was Zach Hyman - Toronto's loss was Edmonton's gain as Zach went to Edmonton for the 22-23 season putting up a career 83 points in his 30 year old season. A team mate who assisted him in that accomplishment was Ryan Nugent Hopkins who in his 29 year old season smashed his prior career bests with a 104 point season.
A major question regarding Tavares has been for his cap hit - was he worth the additional salary compared to his predecessor, previous second line center Nazem Kadri who was traded after Tavares' first season with Toronto. In his second season after the trade, Kadri had a career 87 point season with Colorado as a 31 year old, winning a Stanley cup. Ironically, part of the main difficulties during Kadri's time with Toronto was getting past Boston in the playoffs, a task made more difficult by their top players seeming to improve with age. Brad Marchand scored his first point per game season at 28 - scoring 6 more straight between 29 and 34 - peaking with a 100 point season in his 30 year old season. That season also saw Patrice Bergeron reach his career high in points at 79 (in just 65 games) as a 33 year old and David Krecji match a career high 73 points as a 32 year old. They likely were following the lead of their captain - Zdeno Chara who first reached the 50 point plateau (and his only Norris trophy) at age 30, 10 years earlier.
While unlikely, Toronto fans are likely hoping their stars age like Joe Pavelski - who finally breached the 80 point barrier for the first time in his career in 21-22 as a 37 year old, although one could argue his career year was his 41 goal season at age 29.