CPU-Z only shows nominal voltage of fixed 1.8v.
CPU-Z is reporting the value programmed into the SPD. If someone programmed 3.3V into that SPD field, CPU-Z would report 3.3V.
What would be a more reliable way of finding out what voltage my ram is currently running at?
The BIOS hardware monitoring page, a software utility that can interpret the BIOS hardware monitoring values (e.g. Speed Fan), or a multimeter.