On the subject of whether migration is evidence of the sophistication of the Neanderthals or otherwise:

Given a long enough period very many species of both high and low intelligence have migrated. In our own lifetimes we have observed killer algae migrating from the US to Europe (albeit with a helping hand from man). Algae aren’t that bright, although they are good at survival.

So evidence of migration alone, without evidence for the motives and drivers of the migration, tells us little, other than to reinforce other evidence about the historic climactic range experienced by the location in which the evidence was found.