I'm not sure that the threaded rods make any difference in what the theoretical maximum layer height should be for a given nozzle diameter. No threaded rod is going to make a .25 nozzle lay down a .30 height layer. The reason the layer height should not really be more than 80% of the nozzle diameter is that you need to force each layer into each other just a bit so they stick. If you extrude too high above a subsequent layer, then adhesion is severely affected. Since the nozzles extrude straight down, you can't "push" material backwards against itself to make it thicker than the nozzle diameter.

The threaded rods might affect a "minimum" layer height somehow but I don't think a maximum layer height is affected by them.