Hardware electronic components designed and set for specific pitch change will not cause harmonics (which are what cause the vibrato effect) or if they do a filter can be added to remove it.
As an explanation harmonic frequencies tend to be slightly phase shifted (out of phase with the primary signal) and this is what causes the vibrato/echo. I may have a tin ear, but I do know electronics.
When you are trying to change a pitch by altering the frequency fed to a standard sound card designed for a wide range of frequencies then there is no way to filter out those harmonics completely. This is why I say Electronic Key Change will always be better.
Currently I wouldn't expect them to look at this at this time as they are trying to get a new release out to fix and stablize 4.06 even more first. Maybe in the future they can take another look at it.