Is there a difference between denying the punishment of the grave and not considering it a part of the creed?

The founder of Hizb ut-Tahrir claimed that the proofs for the torment of the grave are probabilistic in their authenticity (ظنية الثبوت), and that it is forbidden to believe in their implications with certainty, though it is permissible to affirm them without absolute conviction. This is because, according to him, certainty would be based on probabilistic evidence. This is a contradiction in his statements, as denial is no different from rejection. Moreover, this opinion contradicts the very principles of the party itself, which stipulate that a successively transmitted report (khabar mutawatir) yields necessary knowledge (ilm al-daruri). The proofs for the torment and bliss of the grave are successively transmitted (mutawatir). Al-Bayhaqi collected many of these, and Al-Kattani mentioned the successive transmission (tawatur) of the questioning by the two angels from 28 Companions, and the torment and bliss of the grave from 32 Companions.