True they should'nt backout either way, but the one with lube will have more pre-strain(clamping force) and whole shebang could get over tightened causing either the bolt to permanently streach(or break) or the tapered part could be shoved together too hard distorting things(or cracking the crank), even though its the same torque. This is because when lube is used less of the resistance comes from thread friction, there for more resistance must come from the ramps(threads are ramps) in order to get the same torque, ramps being a type of lever in a sense.

In some non-bicycle applications more than one torque value is given depending on the type of lube used on the threads, a lower torque for a sliperier lube, I've seen bolts that have permenantly stretched to one and a half times their original length because they used real good lube but the torque spec was calculated for plain 30w oil or even dry threads, this usualy only happens on more highly engineered items like a high performance engine's main bearing studs/bolts where maximum clamping is required, but in a case like the cranks, too much clamping could cause the taper to act similer to a tapered wedge driven into a piece of firewood.
Most large engines(ships) avoid all that by useing a device that pulls straight out on a stud with the correct clamping force then the nut is just screwed on hand tight and when the device is removed the stud has just the right amount of strain for keeping the two parts together.

I prefer long convaluted answers.