I think it's a plothole, if you think that the Mangekyo was awakened for a moment,since we saw when he really awakened the Mangekyo...it maybe a healing technique, that he used to save just Obito's right eye,not his entire body,but I can't imagine his sharingan being the savior, because in that case Obito could have manage to slip through the rock with his entire right part of his body..

I think it's a plot hole. If you think that the Mangekyo was awakened for a moment, since we saw when he really awakened the Mangekyo, it may be a healing technique that he used to save just Obito's right eye, not his entire body. But I can't imagine his Sharingan being the savior because in that case Obito could have managed to slip through the rock with his entire right part of his body.