As I suspected :-) Also note that by measuring "36W POE consumption" you are excluding the AC-DC conversion losses from the switch's PSU which further makes the comparison a bit unfair. IOW your POE equipment draws more than 36W at the wall.
The only fair comparison is looking as only your NAS idling with drives (35W you claim, and I still believe it's closer to 40W) vs the OP's NAS with 4 drives (which should be 57W, or 67W minus 10W for his two extra drives). Then if the OP used a better sized PSU he might cut out another 10W or so (see my "PS" above) then you are comparing your 35W (or 40W) with his 47W which of course is still in your favor and a testament that Ubiquiti did a great job optimizing the UNAS Pro. But this 12W (or 7W) difference hardly matters for someone running a single NAS at their house. This extra power is around $1 or $2 monthly at average US domestic electricity rates.