I'm glad you now understand. I'm trying to help you should you make another guide. Typically, anything that looks distasteful on this site gets frowned upon. Morello's for a tank is an example. One thing that would help would be a Core Items section. What you know you'll be getting regardless of team comp. My core would be Sunfire Cape, because it helps her push and farm creeps better, especially for the less skilled players. Also, Banshee's veil is more or less the best defensive item in the game. Then of course Mercury Treads are almost always a must (because this game revolves around cc). Hope to see more guides from you though.

again codex +kindlegem is a guick 20% CDR like the quickest you can get. that means early game you have

-20% CDR
-+200 health
-gold/10
-health/mana regen
-m resist
-tenacity

with more or less 3k gold.

if you are going to upgrade to morellos or surelias or even consider buying these items as i say on my guide IS OPTIONAL. in my last game i just skilled morello's and went for m resist that we really needed.

The item build is the core items + some suggestions i CANT predict what the opposing team will have thats why i have a guide on what to take on ITEMS section according to what you are facing.

Anyway its your opinion i respect it and move on :)

Frozen Heart is an aura, and someone needs it on your team if you have ANY dps on the other team. Leona is the tank, so this comes naturally for her. The CDR on Frozen Heart is just an added bonus. Also, I never find that I have to worry about mana for Leona. FH and Banshee's pretty much cover my mana needs without a problem. Also, I would rather lose tenacity than waste money on a useless extra item. Also, just like you said, there will be times when you won't need tenacity, and there'll be times when you don't need armor. During these times, you should go strictly for Mres. If Morello's gave you any tankiness at all, I would concur.
I didn't downvote your guide because of that item. I downvoted it because it's very inconvenient. You basically force the reader to take in the whole guide at once. The reason the item builder is there is to give the reader a better understanding of what to usually take, and all you have in it is a bunch of garbage. Your items section was okay. Some things I would change, but okay. In order for your guide to have a good rating, it has to be a good guide. I won't be the only one to downvote this guide, I assure you, given it hasn't been dug into the ground by other guides. And at least I'm giving you my reason instead of just posting "potato" as my comment (which I could've done). My guide got annihilated by votes before I even saw yours.

tl;dr: Your guide needs more tank and auras, and I could care less about the score of my guide. I make them because they're fun.

if you buy frozen heart +ionian boots or whatever you waste money. because with ionian boots you waste a perfect slot for mercury's with frozenheart a perfect slot for thornmail NOT TO MENTION THAT YOU DONT ALWAYS NEED ARMOR and they are MORE EXPENSIVE so you waste money by buying these things. i know her ap values are **** but this item gives
mana regen
CDR
and ability power

2/3 are stats you need. i hate people that got just one thing on their mind and they dont even try something. also i mentioned i red capiral letters when you should buy it and when you shouldnt.

EDIT: dont troll other Leona build because you have made one of your own

Ionian Boots + Frozen Heart + Elixir of Brilliance =45%
CDR cap = 40%

No need to waste money on an item you don't need. Her AP values are terrible anyway, so this wouldn't do anything for her except for the Mregen. Soul Shroud anyone? At least you'd be helping your teammates out...