Are item passives implicitly passed on into higher tier items?

Question

When upgrading an item with a passive effect into another item, is this passive still included in the upgraded item, even when not specified? It seems counter-intuitive that it would not, but I am still unsure.

For example, Seeker's Armguard has a passive which grants 0.5 armour and ability power upon killing a unit, stacking up to 30 times. Seeker's Armguard then builds into Zhonya's Hourglass, which does not list the same passive effect (it only has a unique active: stasis). Am I to assume it does in fact include the Seeker's Armguard passive effect and it is just hidden, or that it does not?

Answer 1

In case of Zhonya's Hourglass, the item itself incorporates the passive in form of its +45 to armor which is +5 armor in comparison to the armguard itself.

However, if not explicitly stated otherwise on the item itself, no passives are transferred between upgrades of items.

Answer 2

It is not the case that passives automatically get carried over. If an upgrade does not list the passive, then it is lost. A great example of this is going from Catalyst the Protector, which has the passive "Valor's Reward", while Righteous Glory, which builds out of Catalyst the Protector, does not have the passive Valor's Reward. Owning a Righteous Glory will not give you the health/mana regeneration upon leveling up.