i would 100% agree but that doesnt limit how many slots there can be just need to be in multiples of 4 right?
The CPU only has 4 'select' control lines. With dual-sided DIMMs, one of those lines is tied to each side, which means two 'select' lines per DIMM and that physically limits it to two double-sided DIMMs per channel.
Another problem is that maintaining signal integrity on multi-drop busses at 1600MT/s (32 drops in the case of a pair of 16 chips DIMMs) is very challenging. This is why server motherboards/CPUs need to use registered DIMMs to drive their large memory configurations - takes the load of driving a very large number of DRAM ICs (18-36 chips per DIMM) off the CPU's control pins by making the whole DIMM look like a single load and that allows server boards to have 4-8 DIMMs per channel. The added complexity increases latency by 1-2 cycles and roughly doubles the DIMM's price.