The 20-year-old rookie kept it together when several others could not as he led 54 of the latter 55 laps in Race 34 at the Valo Adelaide 500.
In the end, the margin of victory was 0.9643s after 78 laps around the Adelaide Parklands Circuit.
It was at the same venue back at the start of the 2006 campaign when Whincup, in his first season with Triple Eight, took victory in the Sunday race.
Coincidentally, he prevailed by just under two seconds from Todd Kelly, who was driving for the same team which Mostert now spearheads.
The victory was Whincup's first of a record 124 and counting, with his seven drivers' titles also the present-day benchmark.
Dane drew parallels as he spoke on Feeney's triumph, post-race.
“In 2006 … Jamie was winning his first race here on the Sunday in a Triple Eight car, and with Todd Kelly chasing him down, a second behind, and kept cool under pressure for the last 30-odd laps,” he noted.
“[It was] Just so reminiscent of that, and that was the birth of a champion there, and Broc replicated that this afternoon.
“He beat yesterday's winner – Chaz is a top two or three driver in the championship at the moment, for sure – and he beat him fair and square.”
The anointing of the Queenslander as Whincup's successor was one of Dane's last big decisions as Triple Eight boss before his retirement from competition.
While Feeney won the Super3 Series in 2019 and Super2 Series in 2021, it was a massive call given the hotseat which Car #88 represents, and the youngster has had his struggles in 2022.
He might have finished sixth in the drivers' standings, but it was only two events ago, for example, that he was benched from qualifying at the Bathurst 1000, with Team Manager Mark Dutton making the call to replace him with co-driver Whincup in the rainy conditions.
Dane feels the appointment has now been vindicated.
“I have to thank Paul Morris as well for his input into it as well as Paul Feeney [father] and Broc's family,” he remarked.
“But, we had a plan, [team co-primary sponsor] Red Bull bought into it for me a couple of years ago and backed me and then when Jamie and Jess [Dane, daughter] took over [running the team], they were happy to follow the line that I that I'd set, to be honest.
“It's all come good today; I don't look like a dickhead, so it's good.”
The Irish-Australian is not completely retired from the sport, but insists he is now letting Whincup and Jessica Dane steer the ship.
“I've been to four Supercar races this year,” noted Dane.
“I've been to a lot of GT races as well, but honestly, Jamie, Jessie, and the crew have got on with running the business.
“[I am] Happy to do those things, but I promise you, I'm well and truly in the back seat right now and when they want me to do something, I do it but Jamie and Jessie and the crew are the ones who are running the business.”
Said business has now officially won this year's Supercars teams' and drivers' championships, and the Super2 Series, after also taking out the Great Race less than two months ago, a swag of victories which is unprecedented in the category in a single season.