Language/dialect could also play a part. Humans form very large social groups that share a common language, so even if a culture comes up with a "unique" names

Language/dialect could also play a part. Humans form very large social groups that share a common language, so even if a culture comes up with a "unique" names (e.g. no special "name" words) in a local group, there will still likely be collisions with others in the wider group. There's still a general rule to keep names unique within local groups, and it's weird to intentionally do otherwise (see Pete & Pete). These animals might have "dialects" that only span a small number of individuals, so part of that "uniqueness" may just be dialect. I think you might see something similar in humans if you looked at small scale illiterate cultures in areas with a lot of linguistic diversity (e.g. Papua New Guinea)