I am saying He was hiding secret details about those things as they apply to the mystery of Christ. Details that are now accessible to us for His glory, as would be the case if early Genesis made no sense to modern readers without seeing it through the lens of Christ but resolved into clear focus once one did so.
Here are some scriptures which indicate this is a part of His nature…
and to bring to light what is the administration of the mystery which for ages has been hidden in God who created all things; By referring to this, when you read you can understand my insight into the mystery of Christ, to be specific, that the Gentiles are fellow heirs and fellow members of the body, and fellow partakers of the promise in Christ Jesus through the gospel,
1 Corinthians 2:7
but we speak God’s wisdom in a mystery, the hidden wisdom which God predestined before the ages to our glory;
that is, the mystery which has been hidden from the past ages and generations, but has now been manifested to His saints, to whom God willed to make known what is the riches of the glory of this mystery among the Gentiles, which is Christ in you, the hope of glory.
He made known to us the mystery of His will, according to His kind intention which He purposed in Him with a view to an administration suitable to the fullness of the times, that is, the summing up of all things in Christ, things in the heavens and things on the earth. In Him
that their hearts may be encouraged, having been knit together in love, and attaining to all the wealth that comes from the full assurance of understanding, resulting in a true knowledge of God’s mystery, that is, Christ Himself,
but in the days of the voice of the seventh angel, when he is about to sound, then the mystery of God is finished, as He preached to His servants the prophets.
And He was saying to them, "To you has been given the mystery of the kingdom of God, but those who are outside get everything in parables,
It is the glory of God to conceal a matter; to search out a matter is the glory of kings
So I do think it is entirely consistent with the character of God to have mysteries hidden in His Word, in particular as it relates to Christ. I think it is important to distinguish between good concordism and bad concordism. If either the interpretation of nature is bad (bad science) or the interpretation of the text is bad (bad theology) then its bad concordism. If it doesn’t point to Christ, that’s a red flag that it is not really a part of God’s mystery being revealed in the text. The YEC view actually diminishes Him, for example making the Sabbath about a 24-hour literal day when the truth points so much more to Christ and reveals more of the mystery of God.
With regard to the account of the heavens and the earth (Genesis 1:1-2:4) my studies have led me to the conclusion that it is talking about more than just the natural universe and so making it only about the natural universe is getting it wrong and can force the interpreter to put something there about nature when it is mostly talking about something else. But if one is saying what it is supposed to be as literature, then I would say that creation itself is giving a poem or song to Adam, who recorded or passed it on. I won’t get into all the reasons I come to that conclusion here, but as literature I think that’s what its supposed to be.