Possibility asks whether the proposed event involves a contradiction. Actual occurrence asks whether that event really takes place. Barzakh doctrine requires keeping these questions distinct.
Allah can bring about modes of life and perception not ordinarily observed by us; that establishes possibility. The claim that grave punishment, bliss, and questioning actually occur is then supported through reliable transmitted texts, not by bare possibility alone.
Thus “it is possible” does not independently demonstrate “it occurs,” and “I have not observed it” does not demonstrate “it is impossible.” Both inferences would confuse different kinds of evidence.