StemaOS Devkit Client - Missing rsync

[KnownBugg]

Game information
SteamOS Devkit Client

Flatpak info
[flatpak --version]
Flatpak 1.16.1

[flatpak --gl-drivers]
nvidia-580-126-09
default
host

Problem description
SteamOS Devkit Client does not work because the rsync tool is not available inside the flatpak.
The application requires rsync to work and it would be nice to have it available.

I was able to expose my system rsync to the application with flatpak-spawn as a test and it progressed further but pairing with a dev-kit failed because system rsync can't see necessary files.

Does this issue reproduce with native Steam
Have not tested (probably not though given the problem)

I don't know much about flatpaks but would it be possible to make rsync available?