Zed can stack BCs for CD into AD but I can't stack Morelloss

Why do AD items such as Black Cleaver, Warrior Enchantment, Dusk Blade, and Maw not have unique passives but Morellos and every AP item that gives CDR including Nashors has it as a unique passive. I never actually noticed this before lol. (I knew AP where unique, I just figured all CDR items where, I believe tank items are the same way).

Shit Irelia could stack Tri Forces with the Excess CDR into AD and get a good amount of all the stats (imagine 4 Tri force, boots and Garg stoneplate. Not saying it would be good but it would be cheesy lol.

I've seen Zed's build Duskblade, Boots, and 4 duskblades in my last few games and I was like why, then I thought about it. The 3 Cleavers after the 1st give 64 AD and 400 HP. So with 4 you get 232 AD, up to 287 AD with the Duskblade, 1600 HP from the BCs and 40% (plus the Ult Hat rune for your ult) CDR. Puts you at around 500 or better with runes and base ratios. Not that this is a amazing build or anything, just the idea they can do it is kinda dumb.

I saw this and at 1st thought was, I wonder what it would be like to do it with Morellos, then I soon realized unique passive. I did the Math anyway though for the fun of it. With 3xMorellos, Boots, Void, Deathcap and Blue pot plus Gathering Storm Rune and the 25 you get from using Sorcery on your second set comes out to be 975 AP + Base APs at 40 Mins. 1038 if you happen to make it 50mins. That would be nuts on a backline artillery mage such as Ziggs lol.