Since the "misprint ticket" is from an inside source I assume the concert date was tentative information that got out. I'm sure promoters booked 2-3 dates in some of these cities to gauge public interest and to see how final tour routing was realised.
What I find odd is that if this ticket was from '74 fans would be freaking out big time. There is still some dates and venues that need cataloguing from tours previous to 1975. I'm STILL waiting for the Ziggy Seattle date to be listed at the Paramount Theater. Nobody seems willing to fix this fact.