Hi,
No, unfortunately it’s not possible. It’s a design decision with pluses and minuses. On the minus side, you don’t just get one zip, which has some conveniences. On the plus, though, it means you can easily restore just a single entity and not need to work with a single huge zip.
e.g. Once your site starts growing, the uploads (media) easily become 90%+ of the data of your site. Restoring just your plugins, after a faulty plugin upgrade, then becomes very difficult. UpdraftPlus has users backing up sites as large as 50Gb – trying to move round a 50Gb zip file, when you just want to restore a plugin to its previous version, would not be fun.
Splitting the backup also very significantly reduces the amount of disk I/O and CPU required to make a backup – which becomes very important on shared web hosting, both for reliability, and keeping margin-sensitive web hosting companies happy. (Re-combining the zips into one is a lost cause, if you want your plugin features to work on 99%+ of hosts (which we do!) because of the disk I/O CPU requirements, except for very small sites).
David