One does not refer to Seth, nor Enoch, nor Noah, nor Abraham, nor David, nor the believing thief (also being crucified), as "Christians"; because though (excepting one human other than Jesus) the Spirit may have been with each one of them, and/or upon one, they are never referred to as having the spirit in them. (Num. 11:25,26,28; Is. 44:3; Ezek. 11:19, 36:27; Joel 21:28)
On the day that the epoch of assemblies of summoned-out-ones began, on Pentecost, the Holy Ghost was said to be poured out both upon the believer-disciples, the hagioi (Acts 2:17, viz. Joel 2:28); and as later on described as sealed with the secure assurance of having the Spirit in the saved-ones' hearts (2 Cor. 1:22), and having His Spirit in the inner man (Eph. 3:16).
These regenerated believer-disciples are the ones spoken of by Jesus to Nicodemus (Jn. 3:3, 5, 6) are those who possess a new spiritual being inside their old-man shell, and are unlike any other human who--though believing--have never been born anew. These reborn humans constitute His ekklesia=Church, composed of His kletoi=summoned ones. It was several years later in Antioch (Paul's sending church) that those assembling regularly to Christ's summons, to learn and practice His commands, were titled "Christian" as a profession, just like a meatcutter is titled "butcher," or a dress-maker is called "seamstress."
What we refer to today as a "Christian" may well not be a regenerated believer-disciple confessing The Christ, but merely an unregenerated (not reborn) believer-adherent professors only companying with the ones fully given to The Christ.
I say this, not necessarily in the pejorative sense, but as a known fact since the beginning of the "age of churches"--which age will terminate at the moment we call "the rapture" --in which only the regenerated beings, either physically having died or yet physically alive, will be rejoined to a new spiritual, bloodless, glorified body, and removed from this physical sphere into a spiritual domain of their Anointed One.
The unregenerated believing professors will not be up-taken, but will remain with the host of unbelievers who, in this physical world, will suffer God's retribution for not completely, persistently trusting in Christ's faithfulness, but (at least in part) of their own efforts, their "holiness," to purchase a route into the spiritual Kingdom of The God.
Now, some of these unregenerated "believers" may eventually be converted. Peter was converted after the Crucifixion (see Lk. 22:31-32; conversion at Galilee Jn.21:15-18); and later regenerated on the day of Pentecost when the Spirit was poured out upon a Christ-less kosmos, and into the waiting believer-disciples; scheduled as the Bride of The Christ. However, unlike Peter, these tribulation-saved ones will not be indwelt by the Holy Spirit, though is written that they will be protected by the Spirit.
Such "believers" may, converted after "the rapture," then become used of the Lord during and after the Tribulation, in the same way that pre-Abrahamic Gentiles and Abraham's seeds were used of Jehovah in the ages preceding the "Age of the Churches." They may even still call themselves "Christians," but they will never be a part of the spiritual-born Bride of The Christ.
They will be saved by now-fully trusting in Israel's Messiach, and will be what is now termed as: "Friends of the Bride."
But The Bride will not be subjected to the tribulational wrath of God, will she/it? Because the espoused Bride will have been taken into another dimension, into the sphere of The Kingdom Of The God, where The Christ is also the Absolute, Perfect Ruler, to be His Celestial Consort forever.
(just a little expansion of what you have said above)
You always bring a fresh, wonderful perspective and I love to read your posts!