Getting content type data from twig view template
Blocks don't have the same variables as other entity types do. They will vary in their theme hook implementations. That is why there is no {{ node.field }} concept for blocks, the information does not exist. The same principle applies to Views, Media, Paragraphs and other entities. For example, to reference fields on the paragraph in its template, you wouldn't call {{ node.field_foo }} you would call {{ paragraph.field_foo }}.

Just because a view block is rendering on a node detail page doesn't mean that the same twig template automatically sees a node object.

If the View is building this block display, I would say add the field to the View that you want to output (Author).

If you want to blow your own mind, if the view you have is returning fields on a node, change the display to use the rendered content mode, and choose a display mode (start with Teaser). This approach will allow you to use node--node-type twig templates, as Views is rendering the entity instead of printing fields into the View. The View output is then driven by the display mode on the node type itself and is a much more manageable result in most cases.