No, it isn't a line-to-RCA converter (they are the ones you;re thinking of, which connect onto the speaker outputs), this is an additional module which plugs into a spare slot in the back of the headunit.
What you will find a lot of manufacturers do when they produce their 'own' stereo's is they partner with a manufacturer to have something built for them, or they licence the rights to badge engineer a previous generation of a given manufacturers stereo.
However, to save production costs, they delete the sort of stuff which is plentiful on aftermarket equipment, such as RCA connectors etc. as they are not needed in a 'standard' configuration.
However, it's more expensive to delete these things at circuit-board level (requiring bespoke boards and components etc) so they are produced with the capability of full functionality, but they forego fitting the requisite connectors to save the vital pennies.
Hence, you can buy these plug in modules - the stereo was always capable of doing the job of RCA pre-outs, remote-on switching etc it just lacked the connectivity to do it, because the stereo is produced to meet a certain price point.
