Difference between "Finish up" button and "craft up" command when deploying after Craft 5 upgrade

[jannisborgers]

While upgrading a site to Craft 5 and using the fields/merge and entry-types/merge commands, it’s common to make further content model changes, arriving at a point where the Craft 4 and Craft 5 versions of the site differ significantly.

This might involve manually renaming fields and entry types, especially when the Craft 4 site used nested Matrix, Super Table/Neo and entries fields. Just running the upgrade and merging fields often creates unnecessary field nesting. To flatten this complexity, writing custom content migrations is also often needed.

To test if the deployment to production would run successfully at this point, I downloaded a fresh DB backup from production and re-imported it locally to simulate the state of production right before deploying. Now the "Finish up" button appears when trying to view the site in the browser.

Can anyone explain what the "Finish up" button does, compared to running craft up in the terminal?

• Using the "Finish up" button, the project config changes (field layouts, field names, entry types, removal of matrix blocks due to entrification) are reverted to the state of the database: I get new yaml files with the old fields. Similar to – if not caused by – project-config/rebuild.
• In contrast, craft up does not make any changes to the working directory. It only asks me to run the migrations related to the Craft update, and then asks me to run the migrations generated by the merge command, after which the changes are all there and complete.

My deploy script follows the docs and executes git pull, composer install and craft up in order, so I’m confident that I’m doing it correctly. But I admit that I always thought that the "Finish up" button does the same as running craft up…