Shaykh al-Islam Ibn Taymiyyah—may Allah have mercy on him—answers this question and dispels the doubt, saying:

“A proposition may in itself constitute disbelief—such as denying the obligation of prayer, almsgiving, fasting, or pilgrimage, or declaring fornication, wine, gambling, or marriage to prohibited kin lawful. Yet the person who utters such a proposition might be someone to whom the divine message has not reached; in that case he is not declared an unbeliever. The same applies to one who has newly entered Islam or was raised in some distant desert where the laws of Islam have never reached him: he is not deemed a disbeliever for rejecting something revealed to the Messenger if he does not know that it was revealed to him. The theses of the Jahmiyyah fall under this category, for they deny both what the Lord—exalted be He—is in reality and what Allah revealed to His Messenger.⦗1⦘”

He also said—may Allah have mercy on him:

“The reason for the dispute—meaning the disagreement among Ahl al-Sunnah over declaring individual Jahmiyyah to be unbelievers—is the apparent conflict between the proofs. On the one hand, they find evidences that require applying the rulings of disbelief to them; on the other, they observe among certain individuals who have voiced those doctrines a degree of faith that precludes their being disbelievers. Thus the two sets of proofs seem to clash. In fact, what befell them regarding the general wording in the statements of the Imams is exactly what befell earlier scholars with the general wording of the scriptural texts.

“Whenever they heard the Imams say, ‘Whoever says such-and-such is a disbeliever,’ the listener assumed that this wording included every single person who uttered it. They failed to consider that declaring someone an unbeliever has conditions and impediments that may be absent in the case of a particular individual, and that an unrestricted verdict of disbelief does not entail judging a named person to be an unbeliever unless the conditions are met and the impediments removed. This is clarified by the fact that Imām Aḥmad and the majority of …”