Likely this would have led to every other sync partner conflating the two records. I doubt they built support for "changing primary key" into their system, and

Likely this would have led to every other sync partner conflating the two records. I doubt they built support for "changing primary key" into their system, and even if they tried, once ID 1 meant two things depending on the time of the change, a 2-way sync can't be relied upon (since the timestamps might conflict).