il padrone wrote:...
The way I understand it, stress is built up in steel spokes (or any steel component) when they are bent but not permanently set. They are thus under continual stress as the steel wants to move back into the prior position. This stress contributes to eventual failure. Spokes laced up are crossed over other spokes and this creates a slight bend.
Stress-relieving involves turning this bend into a cold-set (permanent bend) in the spoke. Sheldon Brown describes this well and advocates using an old crank end to flex the spokes at the cross and set the bend in them
This all may be less relevant for a radial-spoked wheel as there are no spoke crossings. The only reason to 'de-stress' the wheel is really to ease the spokes into a good seating as you describe.
See the wheel failure thread as well. Stress relief is mostly about setting the shape of the spoke elbows, the crossings impart such a slight bend that it is unlikely that there is anything close to yield strength at that point. This is bourne out by the fact that spokes rarely if ever break at a crossing point. The Sheldon method is mostly a convenient way of stressing the elbows, with a marginal benefit of setting the shape at the crossing point. The Jobst method works just as well for radial spokes. It may even be more important to stress relieve radial spokes, since they de-tension more at the bottom of the wheel. It may not be so noticeable because most radial spoking is done on fronts, which break spokes less frequently anyway. It might be interesting to confirm if there are proportionally more radial spoke failures to crossed spoke failures in similar circumstances though.