In regards to the never truly saved view, the words, once enlightened - which means to bring to light, to shed light upon or to cause light to shine upon some object, in the sense of illuminating it. John 1:9 describes Jesus, the "true Light," giving light "to every man," but this cannot mean the light of salvation, because not every man is saved. The light either leads to the complete acceptance of Jesus Christ or produces condemnation in those who reject the light.
Hebrews 10:32-36 NAS
32But remember the former days, when, after being enlightened, you endured a great conflict of sufferings, 33partly by being made a public spectacle through reproaches and tribulations, and partly by becoming sharers with those who were so treated. 34For you showed sympathy to the prisoners and accepted joyfully the seizure of your property, knowing that you have for yourselves a better possession and a lasting one. 35Therefore, do not throw away your confidence, which has a great reward. 36For you have need of endurance, so that when you have done the will of God, you may receive what was promised.
And so why wouldn't this passage in the same letter to these same people about what happens to the enlightened person who falls away not be applicable to them?
Hebrews 6:4-6 NAS
4For in the case of those who have once been enlightened and have tasted of the heavenly gift and have been made partakers of the Holy Spirit, 5and have tasted the good word of God and the powers of the age to come, 6and then have fallen away, it is impossible to renew them again to repentance, since they again crucify to themselves the Son of God and put Him to open shame.
The Hebrews have been enlightened unto salvation, not just unto revelation. And these same Hebrews are warned about what happens to enlightened people who fall away. But we're supposed to take the warning given to enlightened saved people as only talking to enlightened not saved people? That's not reasonable.