Well, yeah, but a "Pass through" should really be a Line In, a unitary gain level buffer, and a Line Out. That's if it's a halfway decent design.

A "Y" split puts the impedances of the two devices you are connecting in parallel, which can lead to gain and stability problems on amplifiers, for example.

If installers try selling you a "Y" splitter cable, shoot first and ask for your money back later - you should always look for a buffered Line In - Out of some sort for the best results, isolation and stability. Caliber and Pioneer both do buffered isolation transformers with multiple line outputs for example.