I fail to see why you were posting that, as if it was contrary to the KJV for why I was referencing it. ... If you were meaning to confirm it, I can see that the message in other verses has changed its meaning, but not that highlighted part.
I posted it for no other reason than the fact that many people, including me, have a hard time reading the archaic English of 250 years ago (c. 1769, Benjamin Blayney revision). While I can understand the attraction people have to the traditional, sophisticated, and solemn language in the King James Version (KJV), it's really quite difficult to absorb.
So, I posted from the New English Translation, which is not only super accurate but also much easier to read. And it says exactly the same thing, but using language that people today can more easily understand and apprehend.
For example, the KJV translates Psalm 139:13a like this:
• "For thou hast possessed my reins ..."
Setting aside the archaic nature of the word "thou," why is the psalmist talking about horse tack here? Reins are long straps, usually made of leather, that are attached to a bridle and used to direct a horse for riding. So, how is that related to God covering David in his mother's womb? And what does covering mean, anyway?
But this is what we have to deal with when it comes to old Shakespearean English. Reins didn't refer to horse tack back then. It actually referred to the kidneys or, more broadly, the inner parts of the body (and was typically used figuratively to represent the seat of conscience and reflection, e.g., Rev 2:23, "I am he which searcheth the reins and hearts," KJV).
This is why the New King James Version (1982) translates it as,
• "You formed my inward parts ..."
And the New English Translation (2006) goes even more accurate and translates it as,
• "You made my mind and heart ..."
If you want to say that this translation "confirms" how the KJV translated it, I guess that's fine. Seems a bit weird, but whatever. To me, they both translated it exactly the same; the only difference is that one translated it into 18th-century English while the other translated it into 21st-century English. It certainly hasn't changed its meaning. They used different English words to say exactly the same thing (e.g., "reins" versus "mind and heart").
Notice how the psalmist acknowledges his existence at conception?
Yes, which is clear in the English of both the 18th and 21st centuries. As the NET puts it (Psalm 51:5-6),
"I was guilty of sin from birth, a sinner the moment my mother conceived me. Look, you desire integrity in the inner man; you want me to possess wisdom."
Again, the psalmist acknowledges his existence at conception.