The reason, I suggest, that this is a problem for you is because you have not completely grasped the more profound aspects of Catholic teaching regarding what a human being is. Human nature, in its pristine state is without sin and without sinful tendencies.
Jesus and Mary would be examples of this. All others, all of us, do have a nature that is God created and without sin, but because of original sin we have inherited concupiscence, which is a superimposed faux “nature” that has distorted our real humanity. That distortion of our human nature has made us all prone to sin. We have a tendency towards acting against our real nature, our real good.
To say someone is a “homosexual” is equating them to some aspect of their concupiscence. It would be no different than labeling someone a “thief” because they have a tendency to covet the goods of others, a rapist because they lust after another human or a murderer because they want to be rid of someone from their life.
It must be clear that the sinful state of concupiscence is an “after market” add-on. God did not create that state. Each of us, fundamentally are God created beings who, due to the choices of past humans and our own have changed or distorted the original “factory model” created by God.
Admittedly, the saints all claim to “be sinners.” That is recognition of their own responsibility for the distortion of their God created humanity - the mess of it - that they have made. It does not mean that the human nature that lies within them is basically sinful. That is a Calvinist idea. The Catholic understanding is that human beings were created good, but made choices that distorted that goodness.
To label anyone by their tendencies or proclivities is simply wrong. Calling someone a thief, a rapist, a pedophile, a liar, a murderer as a means of defining what they are is precisely what Jesus told us not to do. It is making a final judgement about them implying that their state of being is fixed and unalterable. They have become their sin and they are condemned by it. It is acting in the role of judge and executioner because it is a claim to know something about them that only God is in a position to know: that they are beyond redemption.
For all of us, no matter what tendencies or proclivities concupiscence draws us towards, we need to realize those are distortions of our basically good human nature that can be overcome by God’s grace.
When we buy into the tendency of human society to condemn its members by labeling them as thieves, rapists, murderers, pedophiles, we are buying into the impotence of human society to do anything about concupiscence. That is because all members of human society - each of us - is helpless against those tendencies. However, God is not helpless.
There is only one human society - the communion of saints (aka the Body of Chrisf) that is not helpless against those tendencies. This one human society is a constant reminder that we are not our concupiscence. We are not to be identified with our distortions but can overcome them and be restored to our true nature.
To directly answer your question:
No the man ought not confess his tendencies (if your assessment is even true) to his future wife because she is likely as powerless as he to do anything about them. The only one who needs to know is God through his priests. As long as the man is taking every means to remain in a state of grace and avoiding giving into concupiscence that is sufficient.
The one thing about marriage is that the man and woman grow deeper in faith and trust as they journey through life. Admissions of this nature may come about as the couple grow in love and remain faithful to each other. The profound nature of marriage is that it is self-revealing and a means towards overcoming all concupiscence towards sanctity, better when both parties view it that way. No marriage starts out with perfect accord between two saints. Both have baggage, but it is their commitment to seeing each other through that makes it a sacrament - a means to God.
Sinful tendencies are not personal sins. We all have them and we all must recognize and overcome them. It takes a great deal of maturity to come to a realization that “I am not like that” is false, but even more maturity to see the need and means (grace) to truly overcome our distorted and false selves.
A great deal of the problem with marriage in the modern world is the false notion that “I am perfect the way I am.” A notion that refuses to take responsibility for changing “in me” what needs to be changed. Far easier to pin the blame elsewhere (genetics, society, him/her, etc.) than to take on the task of becoming “a true saint” and not merely a caracature of one.
If the “gay” man is aware of all this, then when the time comes, when he and his future wife have jointly reached an appropriate level of trust, maturity and love, a deeper self-revealing will occur, but that is up to them, not you.
A bigger concern would be whether either of them are ill-prepared to be married because of a lack of maturity or awareness of what the commitment of marriage really means.