Finding physical evidence in Antarctica seems extremely unlikely. This study does not claim they got to solid ground, or even that they landed on the ice shelves that surround most of the continent.
Similarly there are no artefacts proving that the first explorers to reach the north pole actually did, and there are multiple disputed claims.
There is physical evidence of Polynesian exploration and settlement on the Auckland Islands, south of New Zealand's main islands by 465km of open ocean [1], about 20% of the way to Antarctic soil, so it seems very unlikely that they wouldn't have explored further south. The thing is there's not much there, just ocean until you meet the ice around Antarctica, so there isn't likely to ever be any physical evidence.
You can't say for certain that they did or did not without evidence in either direction. It's not like it would be unlikely for them to have sailed there, they have far long journeys in their history.
You can argue that they may have reached Antarctica with evidence, which is exactly what this study does and provides. History and science are primarily built on evidence and levels of uncertainty, not proof.
Similarly there are no artefacts proving that the first explorers to reach the north pole actually did, and there are multiple disputed claims.
There is physical evidence of Polynesian exploration and settlement on the Auckland Islands, south of New Zealand's main islands by 465km of open ocean [1], about 20% of the way to Antarctic soil, so it seems very unlikely that they wouldn't have explored further south. The thing is there's not much there, just ocean until you meet the ice around Antarctica, so there isn't likely to ever be any physical evidence.
[1] https://en.wikipedia.org/wiki/Auckland_Islands#History