As long as it is possible then it's ok but they should update the information on the Editions Chart, immagine some new potential user who see it the first time. They probably not even try it out, if they think that they can't "extend" the engine and this would be sad. Programmer love the freedom to change something to their needs as long it is possible. But with that Chart it looks too restricted for someone who doesn't know the engine good enough ( and I doubt that someone registers an account for only make one question on the forums ).