All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
We did not find any statement from the people mentioned in the question indicating that they declared the Ottoman Caliphate to be unbelievers. In fact, we do not believe that any scholar of Islam would issue such a Fatwa suggesting a general Takfeer. Takfeer of individuals is a rather grave and serious matter; it should not be done except with the fulfillment of its legitimate conditions and the absence of the legitimate impediments. It is even more serious and graver to declare Takfeer of a group or state.
For more information, please refer to Fataawa 8106 and 87963 about the restrictions and conditions for Takfeer.