Just see an analogy, if it may be helpful:
a professional scholar is a person, who dedicated his life to a grace of curiosity he had conceived at a certain moment of his life, due to some great impression, that had ignited in him this curiosity. Henceforth, all his life is regulated through this curiosity and research, for per definition, a scholar means a cultivator through an ongoing research of a specific curiosity of which he became an expert.
But now imagine a scholar who through laziness, or through satisfaction with the honors he has received as a scholar for just bearing this name, will betray the essence of what a scholar should mean and loses his curiosity, does not cultivate it any more, just repeats as a CD his previous findings an gets salary for that. Cannot one rebuke such a guy: "a scholar who does not cultivate curiosity and does not engage in research accordingly, has denied the essence of his vacation and is worse than a non-scholar, an ordinary man, who just keeps a common non-expert curiosities about things, even if not making those curiosities a life vacation".
Now, to put a question, similar to yours: does such an apostate scholar still remain a scholar? I would say, NO! in essence he does not! He remains a "scholar" only by name, whereas in essence, taken from the perspective of curiosity that ignites soul, is worse than a non-expert common man, for the latter at least did not murder through sloth that, which is such a wonderful and noble feature - curiosity as to the mysteries of reality.
The same stands, I guess, for those Christians who started practicing the commandments of the Lord, started to grow in Christ and cultivate His word, cultivate faith (for faith is not a static givenness, but a dynamic thing that one can increase or decrease depending on one's free efforts), but then "the worries of this life and the deceitfulness of wealth choke the word, made it unfruitful" (Matt 13:22), such ones will be in a worse spiritual condition than non-Chrsitians to be sure; why? Because, the cultivation of the word of God implies cultivation of love not only towards one's household members, but also towards strangers and even towards enemies, but the one who makes one's love wither even towards his household members is worse than a guy who has not started cultivation of the higher, sublime and, one may say, even supra-natural Christian commandments, but at least loves his own household members through a natural human love. Thus, such deniers, of which Paul speaks about, should not be called "believers" any more for how can one be a believer when the word of God bears no fruit in him, if the very term "believer" means to be engaged in cultivation and nurturing of the word of God?
And we know from the Scriptures that "believers" who are such only by name will not be considered as such in the Last Judgment by Him who gave the salvific faith to humans (Matt 7:21-23).