1Co 15:20
But now is Christ risen from the dead, and become the firstfruits of them that slept.
Christ is the firstfruts of them that slept, which applies to all bodies in the grave, and specifically to the faithful dead.
The term "First-fruitS" is PLURAL persons -not single stalks of grain picked at various times over the centuries. There were 144,000 "First-fruits" in Rev. 14:4. These composed the "First resurrection" group event along with "Christ the First-fruits". There can be a few individual persons on a case-by-case basis raised from the dead in scripture who don't necessarily have to be part of that group of 144,000 First-fruits resurrected along with Christ.
Turning to meaningless word distputes to avoid plaining meaning of what is said, is called doting about words to reject what they say.
It could be called disecting and straining over one word in Scripture, while swallowing the others whole.
Jesus Christ is the firstfruits from the dead of all them that sleep, both before and after His resurrection from the dead.
It's also a partially-played word game. It avoids considering all uses of firstfruits in the Bible.
Rom 16:5
Likewise greet the church that is in their house. Salute my wellbeloved Epaenetus, who is the firstfruits of Achaia unto Christ.
1Co 15:23
But every man in his own order: Christ the firstfruits; afterward they that are Christ's at his coming.
Both are single person firstfruits being at the head of a group that follows. In Christ's case, twice we are told He is at the Head of all resurrected bodies from the grave. In Epaenetus' case, he is the first of all born again saints in Achaia.
Neh 10:35
And to bring the firstfruits of our ground, and the firstfruits of all fruit of all trees, year by year, unto the house of the LORD:
Neh 10:37
And that we should bring the firstfruits of our dough, and our offerings, and the fruit of all manner of trees, of wine and of oil, unto the priests, to the chambers of the house of our God; and the tithes of our ground unto the Levites, that the same Levites might have the tithes in all the cities of our tillage.
We also see it applies to fruit trees individually picked for an offering to the Lord. There may be different pieces from kinds of trees in a group, but each is one piece from one tree.
And finally by grammar, we see the same word itself can be translated interchangeably between singular or plural, so that any argument by singular or plural translation is made meaningless:
Deu 18:4
The firstfruit also of thy corn, of thy wine, and of thine oil, and the first of the fleece of thy sheep, shalt thou give him.
Whether firstfruit or fruits, it means the same for a thine of oil, a single fleece of sheep, or bundle of wheat.
Rom 11:16
For if the firstfruit be holy, the lump is also holy: and if the root be holy, so are the branches.
Rev 22:16
I Jesus have sent mine angel to testify unto you these things in the churches. I am the root and the offspring of David, and the bright and morning star.
Jesus Christ is the holy firstfruit, root, and vine at the Head of all resurrections from the dead that follow. First, at His coming with His own saints, and lastly with all the rest of the dead resurrected unto judgment of works.
Col 1:18
And he is the head of the body, the church: who is the beginning, the firstborn from the dead; that in all things he might have the preeminence.
Christ being the firstfruit or fruits (Seeing either translation is correct), is the firstborn from the dead, and at the Head of all resurrected bodies of men and women from the grave.
He is the beginning of bodily resurrections, that He might have the preeminence in all things in heaven, on earth, and under the earth. (He also went to hell to have the preeminence there as well.)
This is the real offence with people trying to prophecy other bodies resurrected before the Lord, whether it be pagans or namers of CHrist, so that Jesus Christ becomes just one of many in a group: Just another stalk of wheat or corn in the bundle...
If this group resurrection of Jesus Christ ideology, is not from a created christ effort to take Him down a peg or two, so that He's not preeminent in all things with God, then it certainly could be useful to those who reject Him as Lord and God.
This unique "First-begotten" title applies only and always to Christ alone as being the FIRST TO ASCEND in a glorified, resurrected body and be face-to-face with God the Father in heaven.
Heb 1:5
For unto which of the angels said he at any time, Thou art my Son, this day have I begotten thee? And again, I will be to him a Father, and he shall be to me a Son?
Heb 1:6
And again, when he bringeth in the firstbegotten into the world, he saith, And let all the angels of God worship him.
The first and only begotten Son of God in the womb coming into the world, is worshipped at the command of God by all His angels. (The angels that sinned didn't worship the firstbegotten coming into the word at birth, nor do inhabitors of the earth that don't believe it...)