Colliam7 you absolutely did the right thing. That diver might be alive today because you did what every buddy is supposed to do, and that is no exaggeration. The very definition of being a buddy is that you put your buddy's safety ahead of the dive itself. What you did can make the difference between someone seemingly OK to ascend being found on the bottom later, and that person diving another day.
Even I, though, would recognize the difference between a diver ascending because they reached the "normal" end of their dive (ie, reaching gas pressure reserve to ascend, or NDL) and "aborting" a dive. If that diver had come over, showed 800psi left, or 1 min NDL, and signaled he was ascending, that would signal a planned dive end. I would not necessarily consider that an aborted dive that needed special attention if he signaled he was OK to ascend.
But, for a truly aborted dive or a risky end-dive situation (say, he showed 400 psi or was at risk for going OOA in my judgment), I would accompany to the boat no matter what the other diver said.