Charlie, you're not hearing things. But coax bettering TOSLINK is not always the case, especially in cheaper chinese DAC's. Before I modded my Zhaolu I felt that TOSLINK made for a better sound. After the mods, and after adding a pulse transformer to the coax digital input it was no contest. The coax blew away the TOSLINK.
It's all in the implementation.
I did try different TOSLINK cables, including the glass ones and couldn't hear a difference between them.