Search results limited to 3 products - why?

On the settings page of this module I can activate this checkbox:

x Fill up with fallback search term
Search terms will always fill up to 3 products even if only one ASIN was entered into the widget.

Why is the number of search results limited to 3 items?

In the code (ProductService.php) always 10 items are requested through the ->searchItems() function:
$request->setItemCount(10);

So 10 search result items are available in drupal database, but still this option limits it to 3?

I do not understand why? Can you explain?
I want to change this and allow displaying up to 10 products on search results (with a simple patch).
What is/was the reason to limit search result to 3 products?