I believe there is an incorrect assumption or premise inherent in your prompt -- that gender is a property of the soul.

The soul and the spiritual is not gendered, but the physical creation had been created with sex or gender present for purposes of reproduction and to fully reflect God's image from our limited 3rd dimension / physical domain.

At the time of Creation, we were living fully in the physical and spiritual realms simultaneously. Humanity was uninhibited by sin or death and could fully commune with the holy, loving, perfect Creator God. However disobeying God's only command in that perfect garden was a rebellion against God's rightful rule. This introduced sin and sin brought 2 deaths. The first death was instant. The connection that allowed us to commune with God directly was broken immediately. The physical human was not intended to or setup to live without this direct relationship with Creator God, so it was that we began to physically die. Thus our sin brought death. And just as God commanded that all things would reproduce after their own kind, Adam and Eve could not help but to reproduce sinful children and this has continued even to today.

So why does Christianity and the Bible argue against transgenderism you may ask? The reason for this is that transgenderism is a further rebellion against the natural way that God created us. I don't claim that there are not some unfortunate people who have gender disphoria or mental illness, this can happen in our broken world. I don't claim there are not some circumstances where a baby is born with both parts in some rare cases, this is another evidence of how broken our world has become after these few thousands of years from original creation to now due to the brokenness introduced by the fall of man. We should do the best we can in those cases (I've read that typically only one set of organs is actually functional at birth in this rare situation). For the gender dysphoria we should work to provide mental health care to move these individuals back to recognizing that they are the correct gender as they were born. To instead accept their departure from reality as truth, we are enjoining them in taking this mistaken belief and translating it into an act of further rebellion against their own nature and thereby against God. This acceptance of their gender lie would also only encouraging them to end up in a permanently disfiguring and sterilizing "treatment" program that will mutilate their body and bring harm to them. In future years if mercy is extended to them that they realize the error of their belief, they will be unable to go back and often the reaction is suicide.

Back to scripture though, I mentioned gender not being a property of the soul. Matthew 22: 23-33 should clear up some of the confusion here as we will be resurrected to be like unto the angels whom are nor gendered and do not reproduce.

23 The same day the Sadducees, who say there is no resurrection, came to Him and asked Him, 24 saying: “Teacher, Moses said that if a man dies, having no children, his brother shall marry his wife and raise up offspring for his brother. 25 Now there were with us seven brothers. The first died after he had married, and having no offspring, left his wife to his brother. 26 Likewise the second also, and the third, even to the seventh. 27 Last of all the woman died also. 28 Therefore, in the resurrection, whose wife of the seven will she be? For they all had her.” 29 Jesus answered and said to them, “You are [f]mistaken, not knowing the Scriptures nor the power of God. 30 For in the resurrection they neither marry nor are given in marriage, but are like angels [g]of God in heaven. 31 But concerning the resurrection of the dead, have you not read what was spoken to you by God, saying, 32 ‘I am the God of Abraham, the God of Isaac, and the God of Jacob’? God is not the God of the dead, but of the living.” 33 And when the multitudes heard this, they were astonished at His teaching.