If you install a fresh 3.5.4, and add a module like PUR, point your browser to the update page, and start the update, it will list a message stating at some point "7 tasks have been executed, for a total of 7 tasks.".

It seems this message is shown when the 7th task is started, not completed. In fact the last task might take a while where nothing in the browser window changes, specifically, where the "start up Magnolia" button is not yet displayed.

When a user first experiences this, he does not know that such a button will follow, and does not know if he should wait or close the browser window or???

Since "7 tasks have been executed, for a total of 7 tasks." implies that all tasks have been finished, it should only display that message when this truly is the case.