Do those who later identify as “ex-Christians” remain saved under the “once saved, always saved” doctrine?

In some Christian traditions, particularly those that hold to the doctrine commonly summarized as “once saved, always saved” (eternal security), salvation is considered permanent and cannot be lost. However, there are cases where individuals who once professed genuine faith in Christ later renounce Christianity and identify themselves as “ex-Christians.” Some even explicitly reject core Christian beliefs they previously affirmed. According to proponents of “once saved, always saved,” are such individuals still considered saved despite their later rejection of the faith? This raises a theological question: - According to proponents of “once saved, always saved,” are such individuals still considered saved despite their later rejection of the faith? - How do supporters of this doctrine interpret passages such as 1 John 2:19 (“They went out from us, but they were not of us...”) in relation to such cases?