Regarding the ReviewedBy schema property. What is the difference between having it nested inside the mainEntityOfPage property, and having it at the same level of the type: Article type?

For example:

Case 1:

| type: Article
|​ author
    | type: Person
    | id: example.com/authorprofile
    | url: example.com/authorprofile
|​ reviewedBy
    | type: Person
    | id: example.com/authorprofile2
    | url: example.com/authorprofile2

Case 2:

| type: Article
|​ author
    | type: Person
    | id: example.com/authorprofile
    | url: example.com/authorprofile
| mainEntityOfPage
    | reviewedBy
        | type: Person
        | id: example.com/authorprofile2
        | url: example.com/authorprofile2

I extracted a couple of examples from the Google Rich Results test and tried checking the documentation, but I cannot find a clear answer yet.

Thanks!

Note: I am in the process of learning structured data.