I'm thinking maybe it's unified memory? They posted "16GB DDR5 + 8GB GDDR6 VRAM" as the specs as RAM. Typically you'd put the GPU-only VRAM together with the GPU, but the GPU has it's own separate row in the specs. Kind of suspicious how they placed those together like that, isn't it?

It's not unified here. The Steam Deck is and does not list them separately.