The final climb is a 7-km effort at an average gradient of 8.7% - the kind of short, punchy ascent that Thomas believes favours other riders.
Since the Planche des Belles Filles featured for the first time on the Tour in 2012, the rider in yellow after that stage went on to win the race - Bradley Wiggins in 2012, Vincenzo Nibali in 2014 and Chris Froome in 2017.
Thomas took full advantage of the terrain to produce brutal acceleration and take fourth place, 1:44 behind Teuns, who snatched his maiden stage win on a grand tour.
"In other teams, guys like Yatesy (Adam Yates) and Richie (Porte), (Nairo) Quintana, those type of guys I think it suits but when you have got form, you have got good form and it will be interesting to see where everyone is". "I felt pretty good. I thought the steep climbs weren't my cup of tea". It was a decent day in the end.
France's Thibaut Pinot, who had been tagged as the pre-stage favourite on an ascent situated 15km from his home town, reacted swiftly in the last 200 metres on asphalt to limit the damage to a two-second loss.
Thomas, on the back foot after being left behind by team-mate and Ineos co-leader Egan Bernal at the finish of stage three in Epernay, showed that he is still the boss.
"It's just unbelievable", said the Italian after taking the overall lead from Frenchman Julian Alaphilippe by just six seconds.
"I just wasn't up to it today, it's a bitter realisation", said Bardet, who has twice finished on the podium but who was the day's biggest loser.
"It feels unusual, to have the yellow jersey on my back feels so odd." said Ciccone.
Just behind this victorious pair the struggle between the contenders to win the Tour de France itself played out when defending champion Geraint Thomas suggested that the doubters who had called him a one-hit wonder after his 2018 win with Sky might be wrong.
"I will try to understand what happened".
Friday's stage is a long 230km run to Chalon-sur-Saone where a bunch sprint finish is expected.