That crossing was from North Asia (Siberia), not East Asia though? Crossing the Bering strait (88 km) seems a lot less demanding than crossing the pacific from East Asia to North America (~7000 km or so).
I think that is the point of the parent. People made numerous crossing between Asia and America as it was and is simple with good canoes (and later kayaks).
Note also that Kamchatka is not that far from Chukotsky and it is not far fetched to think that the Aino peoples from Northern Japan could have some shared cultures with the Yubik peoples, the latter bringing that culture to Northern America and the Indians that had been living there for 10.000 years.
