South Africa and Australia meet on Saturday for the first time since Smith and Warner returned to the international game following their suspension for their part in the episode at Newlands in 2018.
But du Plessis, the South Africa captain, insists his team will not be bringing up the incident on the pitch and reckons "the Australia culture" now "looks likes it is really good."
"I think their records and their performances will speak much louder than a one-off incident," du Plessis said. "I don't think the game will remember them for that.
"Any player as good as them that is taken away from playing at the highest stage will come back extremely motivated. And I think you can see that the two of them are and they are doing well and scoring runs. They are extremely hungry to perform at international cricket again.
"The fact that Australia's been boosted by the two guys coming back into their batting line-up has made them a pretty complete team. There's not many holes in their team now and they've played some really good cricket at this World Cup.
"They are probably better - I won't say people - but if you look at them now you can see as a team, the Australian culture looks like it's really good. So they have learnt from that and they have made themselves stronger for it.
"I think that's a good sign for anyone. All of us make mistakes. It is about how you learn and how you move forward."
South Africa and Australia have played each other since the Cape Town incident. But du Plessis says there was no attempt from his team to try to utilise the episode to try and unsettle their opponents, while Australia were also happy to "get on and play the game."
"There was certainly no talk about the past or bringing up comments," du Plessis said. "As I said back then, and I will say it now, I believe as a team we are a pretty low-key team when it comes to verbals.
Australia is certainly my favourite team to play against. It's a great competition between two fierce nations
"We just try and get on and play the game and certainly the last few games playing against Australia that is exactly the same, the same from them."
When the World Cup schedule was announced, there was a thought that this game - the final group match - might prove pivotal in deciding which sides qualified for the semi-finals. As things have transpired, however, Australia are certain to qualify and South Africa are certain to go home. But du Plessis feels that such is the natural rivalry between the nations that both sides "give it everything."
"For me playing against Australia has always been a great battle because you face a team that's always very competitive. That is what I love about playing against Australia.
"They are a very, very confident team probably right now and we are probably just are a little bit off where we need to be. But, in saying that, once we cross that rope, playing against Australia is certainly my favourite team to play against.
"It's a great competition between two fierce nations. So, yes, they are looking pretty where they are sitting in terms of the World Cup, but we are still going to make sure we give it everything."