It absolutely does. It adds capacitance, which means you need stronger drivers and higher voltage levels, which means you end up with a quadratic power increase

It absolutely does. It adds capacitance, which means you need stronger drivers and higher voltage levels, which means you end up with a quadratic power increase to maintain the same performance. You cannot push a 512-bit wide memory bus like on the M1 Max through a connector and longer PCB traces without massively increasing the power consumption of the interface. Remember, those laptops have a memory bus equivalent to 8-channel traditional DDRx RAM. You'd need 8 SO-DIMM slots just to get the bandwidth, at a huge increase in power. LPDDR RAM isn't even available in modules for this reason; it's designed for low power, and using connectors goes against that design goal.