Please consider:
We know that there are new revelations yet to come:
Daniel 12: 9 And he said, Go thy way Daniel: for the words are closed up and sealed till the time of the end. 10 Many shall be purified, and made white, and tried; but the wicked shall do wickedly: and none of the wicked shall understand, but the wise shall understand.
and in
Revelations 10:8 Then the voice that I had heard from heaven spoke to me again, saying, “Go, take the small scroll that lies open in the hand of the angel standing on the sea and on the land.” 9 And I went to the angel and said, “Give me the small scroll.”
“Take it and eat it,” he said. “It will make your stomach bitter, but in your mouth it will be as sweet as honey.” 10 So I took the small scroll from the angel’s hand and ate it; and it was as sweet as honey in my mouth, but when I had eaten it, my stomach turned bitter. probably telling us of a new interpretation of an old revelation rather than a completely new revelation which might contradict Deuteronomy 4:2 and Revelation 22:18.
In John 16:12, Jesus said: I have yet many things to say unto you, but ye cannot bear them now. Howbeit, when He, the Spirit of truth, is come, He will guide you into all truth. Hence, Jesus knew some truth that He was unable to disclose to us, and He also knew that this truth would someday be disclosed to the Church. In other words, Jesus knew that the Church was going to receive a new revelation in the far future.
So this being the case, I ask: would not GOD bear witness in HIS Word to a revelation that HE intended to give in the future? Well, I think HE would because HE has done it this way before and if so, then wouldn't a person like Paul (who had gone to heaven and learned the whole truth) and John who ate the little bible most likely be under some leading from the Holy Spirit to bear witness in their writings to these hidden heavenly truths so that, when it was time for their public disclosure later on, there would be some scriptural attestation to them?
But Paul and John could not put it in their open writings in such a way as would disclose the secret ahead of time, right? No, the testimony would have to be hidden somehow so that it remained a secret until the right time.
Therefore, Paul and John would hide the testimony in their writings, knowing that until the time of their revelation, their readers would not really understand what they had written, and that would they make up interpretations which would not be entirely true.
It also stands to reason that these false interpretations would endure unopposed by the truth until the general disclosure in the end times, at which time the new proper interpretation would be made known...
As to why HE chose revelations to be sequential and hidden as hints only for sometime, I only have speculation....