Yes, to make it more clear. There is phases of installation and control file say what clients should be run in each phase. So naming is just convention and presence depends on you.

In fact there is two main phases that you can be interested in
1. before package installation ( dialog you usually see during install )
2. after package install ( to deploy configuration on prepared disk )

so as @kobliha write, first phase is just proposal that can user change and second phase is called usually finish and happen before reboot ( not confusing you with second installation stage as it will no longer be valid ).