Those who are saved are saved by what Christ accomplished, not by physical linage.
Then it can't be because they are of Israel, otherwise, all of the Jews must be saved yet they won't be.
God chose the offspring of Jacob for the exact purpose of demonstrating that they are not
saved because they are of the earthly Israel, but because they are of the spiritual seed of Jacob.
The offspring of Jacob regarding salvation, are his spiritual not his physical offspring.
[Rom 9:8 KJV]
8 That is, They which are the children of the flesh, these [are] not the children of God: but the children of the promise are counted for the seed.
The Galatians were not Jews, yet Paul directly ties them to Isaac and Abraham, and declares them children of the promise. Again, it was directed to the Galatians not to physical Jews or Israel.
[Gal 4:28 KJV]
28 Now we, brethren, as Isaac was, are the children of promise.
[Gal 3:29 KJV]
29 And if ye [be] Christ's, then are ye Abraham's seed, and heirs according to the promise.
Yes, in fact, God did have to reserve to Himself all (Jew and gentile) whom He had planned to save. That was God's promise. No one besides those of His promise can be saved whether Jew or Gentile. That is, only those of the promise can/do call upon the name of the Lord but only because they had been saved. The "saved" of your post (above) is the completion of salvation which occurs at the end of time in the full manifestation of the inheritance.
[1Co 15:50 KJV]
50 Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption.
According to you people are prechosen to be saved. No matter what they desire. What we know is that the Sons of faith are Abrahams children and in Christ are heirs according to the promise and serve God in the new way of the Spirit not the old way of the written code. I know Jesus and He knows me if I were chosen by God to be in Him before I was born He would have told me.
Anyone whether Jew or Gentile as reckoned in the days of the Son of Man would have to be blessed by faith through Him. Those who died before Christ entered the world would have to be raised up by Jesus as well as He gathers from the ends of the heavens to the ends of the earth. So they to would be saved through Him. It was by Gods intent He introduced the new covenant to Israel first.
But linage is there in scripture.
The land allotment in scripture per "tribe" suggests linage promised inheritances by God.
These follow/belong to Jesus are cataloged by linage. Its still noted by God even to those in Christ.
saying: "Do not harm the earth or the sea or the trees, until we have sealed the servants of God on their foreheads."
And I heard the number of the sealed, 144,000, sealed from every tribe of the sons of IsraelJacob)
12,000 from the tribe of Judah were sealed,
12,000 from the tribe of Reuben,
12,000 from the tribe of Gad,
12,000 from the tribe of Asher,
12,000 from the tribe of Naphtali,
12,000 from the tribe of Manasseh,
12,000 from the tribe of Simeon,
12,000 from the tribe of Levi,
12,000 from the tribe of Issachar,
12,000 from the tribe of Zebulun,
12,000 from the tribe of Joseph,
12,000 from the tribe of Benjamin were sealed.
We know those cut off of Christ was because of unbelief.
Is it implied that the children of Jacob were the elect because of Gods promise and not all Israel and so they are those out of Israel who believed in Christ Jesus. Other than the many nations blessed through Abraham the man of faith such promises are not found in regard to the gentiles.
If God is inviting the many how can He also be cursing them to remain in unbelief and perish. That's not a invite.