I know that story about Reb Shlomo Zalman, and have heard similar ones,first hand, involving him or other great poskim. I rest my previously stated case, which was that great poskim have been known to defer to other (great) poskim.
I would like to correct a possible misconception here. From the story, it sounds almost as if Reb Shlomo Zalman is mentioning someone else who happens to be a posek. That would not be an accurate representation. Those two great people, Reb Shlomo Zalman and Rav Waldenberg, were good friends and knew each other from their early years.They lived only a few minutes walk from each other and conferred often. Needless to say they had tremendous admiration and respect for each other. They may not have agreed on everything, but that is only natural.