Why do RAM sticks need to be separated in the DIMM slots?

Digital twin 12+2+2 phases VRM solution; Dual Channel DDR5：4*DIMMs with AMD EXPO Memory Module Support; PCIe UD Slot X： PCIe x16 slot with

However, according to the hardware specifications for my laptop, there are only 2 x SODIMM slots available for use I have an additional 1TB SSD

dimm2 slot Lane x8, slot x16 2UEER PCI-E PCI-E Low profile, half length Low profile, half length Lane x4, slot x16 Lane

dimm slot not working However, according to the hardware specifications for my laptop, there are only 2 x SODIMM slots available for use I have an additional 1TB SSD