Does Lethality Stack? Patch 6.22

So the patch has been out for a few days now and I've been trying to figure out how lethality actually works. Reading the patch notes the lethality passive for edge of night and duskblade are both labeled unique passive and lethality with the same stats of 15 lethality. Further, the movement speed is the same and labeled the same. So there is no point in getting both except for the actives right? If so, that means stacking these items isn't efficient. I suppose balance wise this makes sense, but riot I would recommend making some announcement regarding such or at least removing it from the recommended item list. Also, the lethality on ghostblade is labeled lethality, but has different stats, but is still a unique passive. So with this long exposition I arrive at the actual meat of this post: Does lethality stack? All the lethality passives are labeled unique and lethality so logically they don't stack right and the most lethality you can get is 20? So the change was just a huge nerf to armor pen?