12 channel DDR5 is actually 12x32-bit. JEDEC in its wisdom decided to split the 64-bit channels of earlier versions of DDR into 2x 32-bit channels per DIMM. Reaching 768-bit memory buses with DDR5 requires 24 channels.

Whenever I see DDR5 memory channels discussed, I am never sure if the speaker is accounting for the 2x 32-bit channels per DIMM or not.