I am not aware of the 144k being referred to as under the altar
It's a systemic and problematic situation, whereby "church-ianity" ("the wisdom of men" 1 Cor. 2:5) has trained us to think that all of Revelation was written for the far future, even to the point of extracting many prophetic words from Daniel of 2500 years ago, and erroneously applying them to Revelation.
Only men think in the isolated and segmented forms of past, present and future. However, God from His Eternity, thinks in the past, present and future,
all at the same time.
Only by "the mind of Christ within us", are we able to perceive His meanings, through His use of our words of our own language(s).
The book of Daniel was primarily written for the nation of Israel, being the "
Age of Indignation", as the book of Revelation is written primarily for the church, being the manifestation of the
"Age of God's Grace".
Originally, before He sent His Son,
God was inclined to smite the earth with a curse.
If it wasn't for the
joint ministry of the
two anointed witnesses , being John the Baptist and Jesus, God would have ended it all right then and there. Zech. 4:14.
Malachi 4
[
5] Behold, I will send you Elijah the prophet
before the coming of the great and dreadful day of the LORD:
[
6] And he shall turn the heart of the fathers to the children, and the heart of the children to their fathers,
lest I come and smite the earth with a curse.
So then, ever since Jesus' death and resurrection and Pentecost, God does not see any difference between Jew and Gentile. Therefore, under His Age of Grace, through the NC of Jesus, there is no such thing of Jews being separated from the Gentiles as deserving any kind of special favoritism from God. Rom. 10
[
12] For
there is no difference between the Jew and the Greek: for the same Lord over all is rich unto all that call upon him.
Edit: On the day the nation of Israel crucified to death their promised Messiah, all other promises that God prophesied for them, became null and void, and shall not be fulfilled.