If you make an image on Monday and install an application on Tuesday, that application will NOT be backed and and will be lost when you restore the Monday image.
Yes, that is the usual way updates work, so if I had known that back up / restore Win means back up C: (including my own files) I would not have backed up / restored the complete drive but only Win.

As would anything else added to C after the image was made. Bookmarks, email, pictures of grandma, whatever.
Yes, if only I had known that...

That's one of the reasons why it can be advantageous to keep data on a separate partition that you can EXCLUDE from your image. You'd back it up in some separate manner.
Yes, my "real" own data I have on I:. It is not sensefully possible to have my (portable) programs separated from the Win drive (small SSD 256 GB). To lose the installed programs is not very good, but it is acceptable, it is the way it works, there is no other way to not to have them on C:.

Just for reference. Even Microsoft uses the term "Windows Backup". And their version (soon to be eliminated) does the same thing....the entire C: partition, OS, data, and all.
Yes. but it does not get more usful by that for me. So if a some program displays Win wil be deleted and it means the entire drive will be deleted (instead of Win only what it means for me) it completely misleads respectively does not make any sense for me.