When you report on your own experiences - like the warmth of the sun - that report is not itself the experience.
The scary part about an LLM (p-zombie) is that it can report on an experience exactly the same as if it had one, and for all intents and purposes it'd be sufficient for the task at hand.
After all, I don't need to have your experiences to know what you mean.
By conveying, I don't mean conveying the idea of a possible experience, but conveying knowledge about a real experience that a real experiencer had. What is conveyed is not the entire experience which is impossible, what is conveyed is knowledge that is sensible to someone who has similar experiences they can associate it to.
If the report does not correspond to an underlying experience, then it's just a lie. Like if I say to someone "Thank you" after they do me a favor, they perceive that I am having the experience of gratitude. But if I am not really grateful, then my words haven't conveyed information about an actual experience, about an actual instance of an experience.
So I'd say the report + the report's correspondence to reality + the receiver's ability to understand the report based on their own experiences = conveyance.
I do not consider a false report that leads the receiver to imagine the existence of a non-existent experience to be "conveyance of an experience".
Contemporarily we have methods like radical honesty - another moral absolutist take that also asserts a primacy of truth, that as long as you tell the truth, you can do no wrong
For a lie always harms another; if not some human being, then it nevertheless does harm to humanity in general, inasmuch as it vitiates the very source of right... All practical principles of right must contain rigorous truth... Kant
So, that's the moral side of things. Whether or not you believe in truth as a moral compass (or even a component of it or some moral rubrik), I'll leave up to you! What you said:
> But if I am not really grateful, then my words haven't conveyed information about an actual experience
...gets more at the utility of honesty, as a conveyer of experience. While I might argue you still have conveyed an experience (just not one you had), because the references and end experience still happened in the mind of the receiver, the end (target) experience was had.
The invention of lying is largely due to it working just as well (or better than) the truth in the first place. Maybe the first lie was an accident, and evolution took over where only the best liars passed on their ideas.
So that you could even have an experience rich enough to contemplate!