In answer to your question, Aaron - NO.

To me, logic would state that if you are trying to level frets, you would want the neck as straight as possible. No?
-Aaron

if you add a hump in the fretboard, which is what adding relief during leveling will do, then it will likely cause problems down the road for future fret/radius work...unless it is YOU doing it, and you can duplicate the amount of relief exactly.
adding a shim in the neck pocket, or building in a slight neck angle in relation to the body, should be effectively the same as adding "relief" during radiusing/fret install.
i have no problem getting super low action on my guitars that were constructed with level fretboards.

I asked a few questions. To which one are you referring?

I understand there are differing opinions on this topic. Diversity is the spice of life. I get it. I'm just trying to understand if the people using the neck jig are making the necks straight through counter tension between the jig and the truss rod the same way it happens when the guitar is strung up to tension or if the jig is putting relief in the neck. The first one makes more sense to me than the second.

I worked at Warmoth for about a year and before we would radius fretboards we would actually adjust the truss rod for mild to moderate backbow. The reason for this is to purposefully remove slightly more material from the middle of the fretboard. We would refer to it as "radiusing relief into the neck." All Warmoth necks have only a one way truss rod so it was important to be sure that the neck would have enough relief because forcing it forward is not an option. If you have a Warmoth neck and you measure the thickness of the fretboard at the ends and the middle, you will see that the fretboard is slightly thinner in the middle section.