People have known about earlier contacts for a long time. Norse contact at l'anse aux meadows has been established since the late 90s. Trans-bering contact has been known for centuries.
Humans arrived to rapa nui and other Pacific Islands relatively late, many thousands of years after the Holocene began. Stronger evidence of 13th century contact doesn't change anything about our understanding of the early history of the Americas.
You're pooh-poohing this idea a bit to harshly IMO. I almost wonder if your knowledge here may be out of date. You're aware that there's now evidence of the Americas' being populated over 20,000 years ago, right? Footprints in White Sands and now sloth bone carvings in Brazil. Far earlier than the Norse you mention.
AlotOfReading pointed out that 'This theory is based on the hypothesis that humans pre-1500 didn't have any contact with one another.' is not correct by giving examples of how humans pre-1500 did have contact with one another.
That there were people and civilizations in the Americas before then is far from the point.
I'm aware of them (as any archaeologist remotely interested in the early Americas should be), but they're not completely established parts of the chronology, particularly Santa Elina. People tend to be extremely conservative on this subject because there's such a long history of scams, pseudoscience, and unintentionally misleading results that ended up being false. That results in an extremely high standard of evidence sites have to meet.
However, that's a wildly different topic than what the grandparent comment is talking about. I'm interpreting their comment in a charitable light because interpreting it more broadly quickly gets into hyperdiffusionism territory.
The people from over 20,000 years ago came from the northern ice bridge, however. My suggestion is that these people got civilization ideas from the Islanders at around 1500BC. They didn't get a full line of communication with the old world but enough ideas were taken to kick start a civilization.
What "civilization ideas"? How did they get these ideas from an uninhabited island? Easter Island wasn't settled by Polynesians by at least 300 AD.
There is evidence of contact between Polynesian and South America. Like Polynesians having sweet potato. But not enough for visible changes of either one.
Civilization doesn't seem to spread by short contact, only close contact. Civilization is complex so a few ideas aren't enough to spread it. And it is hard for culture to accept that much change.
Rapa nui (and other Eastern Pacific Islands) hadn't been settled yet at that point, while indigenous Americans were already building monumental structures (e.g. Norte Chico) and working metal (old copper complex). The latter predates most metalworking in the old world too.
Their settling is irrelevant as long as they were able to get there. It's possible that they brought the ideas to Norte Chico where a civilization developed before them settling down.
Humans arrived to rapa nui and other Pacific Islands relatively late, many thousands of years after the Holocene began. Stronger evidence of 13th century contact doesn't change anything about our understanding of the early history of the Americas.