I presume that some at least do not take much of the Koran, such as those passages I focused on, literally. Others are probably Muslim by virtue of birth and up-bringing, but are more secular than religious, like many christians and jews.
A truly devout Muslim, however, is presumed to believe that the Koran is the direct word of God spoken to Mohammed. In that case, they must be presumed to believe the passages I quoted. based on what we see going on around the world, that is the inexcapable conclusion. Loyalty to Islam is all that counts, and oaths to other than Islam are made of convenience and not to be taken seriously.