I wouldn't expect it to be. I don't have the "stereo" CD to confirm this, but Amigos was released in both stereo and SQ quad releases during the period when Columbia was doing separate studio sessions specifically to produce the quad releases. So, there would be both an SQ and a stereo master in existence.
It would be highly unusual for them to "choose" the SQ master for the CD if they have a true stereo master available for use.
QuadBob