False PROBLEM PLEASE DELETE

Ever since DDR2, termination has been somewhere on the stick of RAM and not on the motherboard (you could see the resistors on DDR1 motherboards right next to the RAM slots on the side farther away from the Northbridge).

Theoretically, leaving an empty DIMM slot at the end of a channel then instead of a RAM stick could cause noisy reflections from the empty unterminated stub to hurt signal-to-noise. So it should be better to put RAM in the furthest slot from the memory controller. DDR4 obviously doesn't use simple passive terminating resistors but termination still happens somewhere on the stick so I would expect the same should apply.