No, SCEA is NOT ED essentially. ED is closer to a contractual relationship -- you get accepted, you're pretty bound to attend. With SCEA, the only thing you are agreeing to is to not make early action/early decision application elsewhere. If you are accepted SCEA, you are not bound to attend. You can still decide, although having bagged either of Stanford or Yale, maybe you don't want to bother applying and deciding on anywhere else.