Not only doesn’t this surprise me, its not having happened would surprise me:

Polynesians may have sailed to South America at least 100
years before Europeans landed there in the 16th century, according to
research that strengthens theories popularised by the   Kon-Tiki explorer
Thor Heyerdahl. DNA analysis of chicken bones from an archaeological site in
Chile has shown that they share a genetic profile with ancient poultry from
Tonga, Samoa, Hawaii and Easter Island — suggesting that the birds were
introduced from the Pacific.

The human colonization of the Pacific is a story of a group, originally from Taiwan (if I’m remembering Guns Germs and Steel correctly) hopping from island to island, each place inhabited providing the adventurers who got to hte next. Madagascar in 400 AD or so going one way, Hawaii 1,400 AD going the other. That none ever got to South America would be a surprise.

However, that no distinctive Polynesian culture is found in South America, nor any (as yet found at least) DNA evidence amongst the current population would seem to militate against the idea if i were not for this one point. Many of the island groups were inhabited by small groups that simply found them. But as with the Vikings coming from the other direction to Vinland, it’s a great deal easier to do that if there aren’t already other human beings there occupying the same ecological niche that you want to.