Apple has two operating systems: macOS and iOS.
SyncBack Touch supports macOS but not iOS
macOS is the big lifter and can be found on Apple’s computers including: iMac; MacBook Air/Pro; Mac Pro; Mac Mini.
iOS is a mobile operating system for Apple’s iDevices including: iPhone; iPad/Air/Mini; Apple TV; and iPod Touch.
In iOS each application is “sandboxed” - a security mechanism for separating running programs. Sandboxing controls the resources (for example, file descriptors, memory, file system space, etc.) that a process is allowed to use. Each application remains isolated. SyncBack Touch would not be able to backup files created by other applications in iOS as it too would be sandboxed (kept isolated from all other applications).
Unfortunately these technical constraints by Apple render SyncBack Touch impractical for iOS unless there is a major change in Apple's policy on how much freedom they give to applications.