Currently, the "Checking for updates..." dialog box that appears when accessing File > Check for updates... looks like this when applying updates are done.

In my opinion, I think it is a good idea to have the dialog title (where the "Checking for updates..." text is) say "Updates applied." when there are updates and "No new updates." when there are no updates found. This textual change is significant and would give users the impression that updates are indeed completed compared to just making the percentage be 100%, which would make it harder to tell since users may think that the updates are still being applied and aren’t done.
Currently, the "Checking for updates..." dialog box that appears when accessing File > Check for updates... looks like this when applying updates are done.

In my opinion, I think it is a good idea to have the dialog title (where the "Checking for updates..." text is) say "Updates applied." when there are updates and "No new updates." when there are no updates found. This textual change is significant and would give users the impression that updates are indeed completed compared to just making the percentage be 100%, which would make it harder to tell since users may think that the updates are still being applied and aren’t done.