EMAS at RESA/SWY is usually marked with yellow chevrons — it's not very hard obtainable from satellite imagery. But yes, the markings may not have been applied at the time of the satellite imagery for some reason.
1. Yes, AIPs are government documents. But as everywhere, there can be errors, as well as outdated information. For example, in Nalchik AIP chart with 15 parking positions for today, but de facto there are 16 and the de facto parking lanes has been changed.
2. I have no desire to develop new aero marking schemes in OSM wiki. I'm marking objects of my interest in according to the current OSM wiki description. At the moment aeroway=stopway on the wiki corresponds to a way-type object where there is EMAS coverage on RESA (e.g. Barajas) or on SWY (e.g. Badajoz).
However, I am willing to answer your questions if there is anything I would know.
OpenStreetMap