When you put a requirement as “direct experience” to “parinibbāna” (which by definition: can only be talked about after the “death” of an arahant), I suppose that you were running into a kind of dilemma like: If the Buddha has not “direct experienced” and he can’t lie, so, he can’t claim about “parinibbāna”. On the other hand, if the Buddha had really direct experienced “parinibbāna”, then he is already so called “surely dead”, it will be impossible for him to claim anything after “surely dead”.
I have given you a “theory” which is: the Buddha really “direct experienced” the “parinibbāna”, but it’s not his “parinibbāna”, instead, he “direct experienced” the “parinibbāna” of many many previous Buddhas and many many previous noble disciplines. This is due to the awakening of his first two powers: the power to see unlimitedly into his past lives and the power to see unlimitedly into other past lives’s kamma. These two powers are “direct experienced”, these are not conceptual understanding.
Finally, with the awakening of his 3rd power: he see for himself the destruction of all defilements, again, this 3rd power is not conceptual understanding.
As I said, because he already had “direct experienced” that so many many previous Buddhas and so many many noble disciplines with the destruction of all defilements have “entered into” parinibbāna, combining that with his also “direct experienced” of his 3rd power, he comes to concrete conclusion: he will surely enter into parinibbāna after “death”.
If you ask yourself this question: “Will I die?”. Even though you don’t have “direct experience” of death for yourself, do you know with 100% certainty that you will die? I think anyone with a reasonable mind will have to answer with 100% certainty that: “Yes, I will die”.
The next question is: “How do you know? You don’t have “direct experience” of your own death, right?”. Again, I think anyone with a reasonable mind will have to answer that “I see everyone around me die and because I am not so different from everyone else, I will die too”
Now, if you compare with the “direct experience” of the Buddha due to his 3 powers, you can see that his certainty is even greater than your 100% certainty about “I will die”. The reason is: He directly experienced his own death for so many many past lives.
Again, if you compare with the “direct experience” of the Buddha due to his 3 powers, you can see that his certainty is even greater than your 100% certainty about “I will die”. The reason is: He directly experienced other’s parinibbāna for so many many past lives.
Again, if you compare with the “direct experience” of the Buddha due to his 3 powers, you can see that his certainty is even greater than your 100% certainty about “I will die”. The reason is: He directly experienced his own destruction of defilement, he is no different from previous Buddha, therefore, similar to your own reasoning with 100% certainty “I see everyone around me die and because I am not so different from everyone else, I will die too”, he can come to conclusion with 100% certainty: “I see everyone around me with destruction of defilement entered into parinibbāna and because I am not different from these people, I will also enter into parinibbāna”
I hope that I have answered to your question that it was really a direct experience and the Buddha’s conclusion is even more certain than your own conclusion that “I will die”. If you haven’t directly experienced these 3 powers by yourself, I think, it’s too hasty from your part to come to such a conclusion as “that is indirect meditative perception”.
Anyway, as I said in the beginning, this is just a theory, no matter how soundly, logically, completely or coherently a theory is, we still can’t accurately say what belongs to the Buddha’s domain (just a quick reminder of Acinteyyasutta AN 4.77)