Something that is not obvious is that the elevations are not required to be "real" in Network Analysis. As they describe in the process you ran in step 20, one can use logical elevations besides real elevations. The important thing is that the values chosen for the segment ends are exactly the same for segments that should connect. Any values could be used, as long as the connecting values are the same. So by using logical elevations one could choose 1, 6, 2657429, or 99 - as long as the value is the same for the segments ends that connect. For example, in its simplest form, if one had a network with ground level and one level of overpasses, one could take a binary approach and do a whole network with just 0 and 1 for elevation values - a value of zero for ground level and a value of one for overpass segments.
One could also do a more rigorous analysis and derive the actual true elevations for each segment end. However, the catch is the values will still need to be exactly the same for each segment that connects, and this could involve a bit of cleanup.
If you are only after connectivity for Network Analysis, I'd suggest using logical elevations over true elevations.
Chris Donohue, GISP