It's not the same as Sooloos; Tidal supports 'offline' mode on mobile streaming devices such as phones so that the selected tracks can be played even when there is no signal. To enable this it has to download the [encrypted] tracks.

861v6+ID40, HD621, 8000.2, 7200HC, 7200.2, SKYQ Silver, PS3, PDP-LX6090, QNAP TS870-Pro (8*6TB), Roon, iPadAir2.
[In Reserve] C15, MD600 (2*3TB), TwinStore RM (2*2TB)