If I understand what happened, this sounds like a clerk working to make an amendment at their level, rather than pushing it to someone with Correction mode access.
The acts of cancelling and republishing the promotion each triggered a pay action - the first to recover the acting pay, the second to reissue it.
I think the better approach probably would have been to have a senior clerk with Correction mode access to change the data in the promotion row from Acting to Substantive, which would not have triggered CCPS action. That said, I'm not positive whether such a change is possible.