Pardon me but 2. Peter. 2.20 does not say such a one is saved, it says they knew the path of righteousness but turned away from it.
2Pe 2:20 For if after they have escaped the pollutions of the world through the knowledge of the Lord and Saviour Jesus Christ, they are again entangled therein, and overcome, the latter end is worse with them than the beginning.
2Pe 2:21 For it had been better for them not to have known the way of righteousness, than, after they have known it, to turn from the holy commandment delivered unto them.
2Pe 2:22 But it is happened unto them according to the true proverb, The dog is turned to his own vomit again; and the sow that was washed to her wallowing in the mire.
This is talking about people that escaped the pollutions of the world through the knowledge of the Lord and Savior Jesus Christ.
They had the knowledge of the Lord Jesus Christ that He is Savior and a person can only escape the pollutions of the world by Jesus Christ.
They got tangled back in the world and became worse than at the beginning before they were saved.
They escaped the world which no one can do unless they were saved by Jesus.
But it would of been better for them if they had not known the way of righteousness then after knowing it to turn from the holy commandment given to them.
They knew the way of righteousness and the holy commandment but turned from that.
They escaped the world by the knowledge of Jesus Christ the Savior.
They knew the way of righteousness.
They had the holy commandment delivered to them.
This obviously can only apply to a person that has been saved.
But they turned form those things by going back to the pollutions of the world and got entangled in it and were worse which is like a sow that was clean wen back to wallowing in mud and becoming dirty.
This obviously without a doubt is talking about a person saved and then losing salvation because when they turned from the truth it would of had better if they had known the truth than to turn from.
That does not sound good that it would of had been better for them to not have known the truth than to turn from it and we know people that do not know the truth shall still be punished for not turning to the truth.
It is obvious they lost salvation and since it is a warning to the saints then it could happen if people play with fire and go back to their old lifestyle.
Which remember Lot's wife how she turned back and turned in to a pillar of salt.
And Jesus said any person putting their hand to the plow and looks back is unfit for the kingdom of God.
Which means that anyone that starts living for the kingdom of God and looks back to a life of sin which is going back to the world is unfit for the kingdom of God.
More warnings so a person can lose salvation for why would there be warnings if it were not possible.
It is obvious without a doubt that it is talking about people that were saved being tangled again in the world and losing salvation because they became like the world again which is unclean.
People will defend their beliefs tooth and nail and do not want to hear scriptures the way that it reads.