Using Syncthing for One-Way Transfers

I’m looking into a backup solution for my family’s photos/phones. I’m familiar with Syncthing so I installed it our NAS server. The goal is our phones will transparently send new files to the server and allow us to delete files to make space on the phones.

Surprisingly, this one-way data transfer is not recommended by Syncthing but it can be done by configuring the phone to send only mode, the server to receive only mode and finding the hidden advanced option on the server to ignore deletes.

The name is Syncthing so I suppose I am trying to use it wrong.

Read more details on their forums here.

EDIT: I am questioning this workflow and suspect it is more complicated than just a normal two-way sync plus periodically pruning and copying files to the directory I setup in the NAS for backups. I would like to learn more about setups that work for others.