Here is the developer’s response to your questions:
We are setting the order in WP_Query and performing an AJAX query to update the results with the new order.
We have several query arguments they can check to detect if the query is related to the filter grid. Here is an example:
isset( $query->query[‘dfg_context’] )
dfg_context can have multiple values. If the argument exists at all, it is coming from Divi FilterGrid.