the normal backup saves a list of installed apps - not the apps themselves.

so if you restore the backup you have to download all those apps again - but this is done automatically

i can't imagine any other solution for doing a backup of all apps.

edit: ok... you may be able to save all deb-files out of the archives-folder. but you'll have to update these apps anyways. so the backup-tool is (in my opinion) the best way. ^^