A 135 Contention - it's open to debate, but Troacctid's response is a good one to go with.

Troacctid's response is the obvious one, neither ability lists a bonus type therefore they are untyped and stack - and most DM's will agree with this which is fine (and I suspect it's the author's intention); however they don't need to list a bonus type because they already have one!
Quote Originally Posted by SRD: Modifiers
Modifier Types
Ability Modifier: The bonus or penalty associated with a particular ability score. Ability modifiers apply to die rolls for character actions involving the corresponding abilities.
The type "Ability Modifier" is literally the first entry in the modifiers section.

So, am I saying 'They are both "[Ability=Charisma] Modifiers" and thus don't stack?' Well it's still debatable so I am not saying that either!

Firstly the type is "Ability" not "Strength", "Dexterity", … or "Charisma" which suggests you cannot stack modifiers from different characteristics to the same result and no one plays that (I think).

Secondly the SRD states "Ability modifiers apply to die rolls for character actions" and Armor Class is not a die roll, which strongly implies that "Ability Modifier" is not a valid modifier type for armor class (which has horrible implications for the Dexterity bonus to AC which is explicitly allowed).

Thirdly, untyped bonuses only stack if they are from different sources, so is the source the special ability (Apparent Defense / Unearthly Grace) or the characteristic ability (Charisma)?

So, it comes down to what the DM and table are happy with. Allowing them to stack is fine, but it is not unreasonable to say no, they don't stack because they are both Charisma.
The rules are ambiguous on this (English being ambiguous even when you try to be precise).