Why is the process of reissuing a ticket due to a schedule change so ... incremental, for want of a better word ... post-3/3?

I called earlier today to fix an international misconnect due to a schedule change. The call itself was very smooth; I gave the agent the PNR and the problem flight + my preferred alternative. After putting me on hold for about 5 minutes, she had it taken care of and took my seat assignment, and we were done.

Now, online, I have seen the reservation go through several stages. (At every stage, it has claimed "a change has been made ... please call" etc.) First, the new flight showed up in W, in addition to the old segment (which was W but upgraded into R--and yes, the alternate flight has R2 at the moment, so the upgrade should transfer).

Next, the problem segment vanished from my itin (as it should), but now all of the segments are out of order--I have one of the outbound segments listed at the very end of the itin, and that was one which shouldn't have been touched, anyway.

Then the segments got back in the right order, but still with W for the new segment.

Finally, the itin is 100% correct, with R for the new segment, all segments in the right order, the "please call" message gone, etc.

The fact that things are so iterative is a bit odd.