"How certain are we when we point a finger to suggest there is a steroid culture in a country that has just won the World Cup? Fairly certain," Francis wrote in the Irish Independent.
"What were we saying about latitude and dispensation? Do we need to put an asterisk beside the winners of the 2019 World Cup?"
Wentzel, who played for South Africa in 2002, told Sport24 it was difficult to argue against the claims with the South African rugby schoolboy scene presenting an alarming doping problem.
"The unfortunate fact is that if we look at the last few years in terms of the amount of rugby players caught doping, critics have a point," Wentzel told Sport24.
"In recent times we have had the cases of Gerbrandt Grobler, Chiliboy Ralepelle and Aphiwe Dyantyi and way back we had the likes of Johan Ackermann. It's an issue and I don't think those who raise the issue are factually incorrect."
Grobler, who played with Western Province, and Ralepelle both missed multiple seasons after testing positive in drug tests.
Most recently, 2018 World Rugby Breakthrough Player of the Year Dyantyi tested positive to banned substances.
Wentzel was shocked to learn about the doping culture in schoolboy rugby, with last year's drug testing at the annual Craven Week tournament recording six positive findings for steroids.
He said it would be hard to reverse the trend with the highly competitive standard of schoolboy rugby demanding "massive" players.
"From what one hears the steroid use at schoolboy level is quite rife but is it because we are so competitive and there are so many players? It might spring from that because rugby is such a big cultural phenomenon," Wentzel said.
"It is up to the coaches and parents to police the use of steroids but kids are kids. In today's age you can't stop them and if they want something they'll get it."
The Springboks sent fans on social media into meltdown shortly before the start of the Rugby World Cup in Japan, with a team picture showing off their chiselled upper bodies.
The Boks beat England 32-12 in the final to claim a third Webb Ellis trophy.