All of these descriptions can be for those who experienced Jesus' ministry, the works the Holy Spirit empowered Him to do showing a taste of the Kingdom. To hear the Very Son of God preach the Word of His Father! Healed by Him, taught by Him, devils cast out, sending out the 70, each partakers of the Holy Spirit, each tasting those powers,You say: "But this passage doesn't come out and say that those who are God's children can become lost again. And if you interpret it as saying that, you run smack into those passages that tell us that doesn't happen."
Really? Read it again.
4 For it is impossible for those who were once enlightened, and have tasted the heavenly gift, and have become partakers of the Holy Spirit, 5 and have tasted the good word of God and the powers of the age to come, 6 if they fall away, to renew them again to repentance, since they crucify again for themselves the Son of God, and put Him to an open shame.
No, there's nothing here that specifically says these were born again, there are the Pharisees, whom Jesus warned, your sin may never be forgiven!
But again, the matter is settled in the text,
4 For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost,
5 And have tasted the good word of God, and the powers of the world to come,
6 If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame.
7 For the earth which drinketh in the rain that cometh oft upon it, and bringeth forth herbs meet for them by whom it is dressed, receiveth blessing from God:
8 But that which beareth thorns and briers is rejected, and is nigh unto cursing; whose end is to be burned.
9 But, beloved, we are persuaded better things of you, and things that accompany salvation, though we thus speak.
Better things of you, and things that accompany salvation.
Either the fruitful herb grows or thorny brier grows. The writer says, I think you're the "salvation" plant.
Much love!