Popular travel day and time and DL is not currently releasing any inventory in U/T/X/V fare classes on flights. BE fares are dual inventory fares and only go as high as U class on this route. With only L and higher fare bucket open in coach fare classes, there are only Main Cabin fares to choose from due to dual inventory preventing any of the BE fare filings from being booked. No, there is no way to get Google Flights to filter out BE fares. ITA Matrix can do it though with advanced controls (F ~BC=E in extension codes, DL+ in routing codes to limit it to DL flights).