What is the industry term for this effect?
It's a pointer
The Callout, if it is used within other text, has a "pointer" as illustrated above. It is shaded in your illustration and has a rule to give it a 3D appearance. (The red arrow is also a pointer.) If it is just a design element, boxed as you show, used for some impact; I'd call it a design element.
Usually, a callout brings the reader's attention to text that is used in the article (copy) by setting it with some sort of emphasis. There can be many different ways to emphasize a callout. Your example uses a pointer. Bearers can also be used.
If it does not repeat text within the article, it is not a callout. It is text set within an attention-getting border. As you show it without the rest of the article, it is not a callout.
Callout is the most common term I know of. You used it in your question. Regardless of whether it indicates a source or not, it's still referred to as a callout.