Saul didn't truly know Jesus, but nether do many who reject Jesus in this life.
No one comes to Jesus unless the father draws them, and they are drawn by the conviction of the Holy Spirit. John 16:8 That is not the baptism of the Holy Spirit, for that to come requires follow through.
A video I watched recently provides some evidence if you are willing to watch.
Many believe in Jesus Christ but they do not know him, they say Lord Lord but their hearts are far from him.
Born again (Baptised in the Holy Spirit) is about becoming an Israel, a Servant of God, not a baptised believer that is only like Judah, a people of God.
Jacob was saved when he became Israel, he was separated for God.
Not all of Israel are of God or Servants of God, because they are only of the Tribe of Israel, not like Jacob who was Israel a servant of God.
Death bed conversions are sad, but do carry some worth but fact is if Grace does not abound your lost. I am not saying who is going to Heaven that's not up to me, but big deal some twerp ranting against Jesus was never saved in the first place and would of murdered Jesus if they could of. Narrow is the Gate and there is few, remember, not wide and a lot.
How many evil moronic Atheist have I herd say, on their death bed they will just repent and this crap is peddled as gold by fools, with a big stupid smile.
Grace confers holiness and changes the sinner into the friend of God, it is this grace witch is the basis for the virtues and the gifts of the Holy Spirit, it's a gift to the intellect, enlightens the mind and strengthens the will.
Grace is absolutely necessary.