I wouldn't necessarily agree with that. The Gentiles were not officially included until Cornelius, and even then there was discussions.
I would say that The Gentiles were included as early as the OT on the basis of grace through faith.
For all practical purposes, Abraham was just another guy (nations) until he was separated by God. If he was an Iraqi the day before, then what were the other Iraqis the day after?
What do you think “The Court of the Gentiles” is about in the Temple? Jesus said, “My House shall be called a House of Prayer for the ETHNOI (Gentiles) but you have made it a den of thieves.”
They were cheating, buying, and selling....bad.
They were also doing so in the location for Gentile worship....also bad.
Gentile worship?
Didn’t think that happened until Pentecost.