I just looked at the AA SDFC web page (https://www.aa.com/i18n/plan-travel/...day-travel.jsp) and it no longer references E space availability, just says "On select routes operated and marketed by American or American Eagle, based on availability" and "Offer is made at our discretion and subject to change or termination at any time." I had to SDFC just two weeks ago, and I'm fairly certain the page referenced E space then.