Comma usage with names ?

Online source:

I went to see the movie, “Midnight in Paris” with my friend, Jessie.

Comma after “movie,” comma after “friend” and, sometimes, comma after “Paris” as well. None are correct — unless “Midnight in Paris” is the only movie in the world and Jessie is the writer’s only friend. Otherwise, the punctuation should be:

I went to see the movie “Midnight in Paris” with my friend Jessie.

So the statement in bold says the sentence is correct if it is the only movie in the world and Jessie is the writers only friend. And we fix this by omitting the commas if it isn't, and adding them if the sentence is structured like this:

I went to see Woody Allen’s latest movie, “Midnight in Paris,” with my oldest friend, Jessie.

Question:

1: Why does a comma just before the name Jesse suggest that is the writers only friend. I can see 'oldest' refering to his oldest friend so requiring a comma. The writer has suggested the first example is wrong but right if it is his only friend.

source:

One helpful set of terms is essential vs. nonessential. When the identifier makes sense in the sentence by itself, then the name is nonessential and you use a comma before it. Otherwise, no comma. That explains an exception to the only-thing-in-the-world rule: when the words “a,” “an” or “some,” or a number, come before the description or identification of a name, use a comma.

What would be an example of using some or a number before a name? The name not:

• Some examples, like this one, are self-referential.

• Two self-referential examples, the last one and this one, appear in this answer.

Question:

I see usage with 'one' comma often in papers for instance. So what are we saying here by placing one comma before the names? So it's wrong not to use a comma? We have a volunteer Lucy and Jenny and her partner Steven: I don't see why they need commas ?

Volunteer, Lucy has set out to arrange a charity run.

Jenny and her partner, Steven would instead be attached as potential owners.