It’s time we stop playing these ridiculous games. You’re in shidduchim? You’re going out? Submit your numbers to Dor Yeshorim before meeting even once. I have yet to hear a cogent argument to the contrary.Life is complicated. The whole reason Dor Yesharim operates confidentially, and won't even tell people themselves that they are carriers (unless they match up with each other) is because of stupid stigma in certain ignorant, closed-minded frum Jewish communities. If a chassan or kallah knows he or she is a carrier, they might be obligated to tell the other party, even as a non-carrier, and this could mess up the shidduch. And if you compare Dor Yesharim numbers for every potential shidduch, before even beginning dating, then the likelihood increases that you will find out that you are a carrier. For at that point Dor Yesharim will say "no", and will inform both parties what they are carriers for. Then, the shadchan will know that the potential chassan and kallah are carriers for some genetic disease, and perhaps even the particular disease. Then, the shadchan may be less likely to set the person up, or may casually tell someone else, messing up the chassan and kallah's shidduch chances. Furthermore, the family of the chassan and kallah may then know just what the other person has. And the person himself will know he is a carrier, with the possible obligation to inform others of this status. And all this would not be the end of the world if people were not idiots. But they are, or else Dor Yesharim would not need to act so secretively.
Also, Dor Yesharim have expanded their tests to include things for which would not necessarily be disastrous, where the symptoms wouldn't be so terrible and the chance of having it would be fairly low, despite being carriers. The boy and girl could possibly really like each other, and choose to go through with the shidduch now that they know each other. But if they never knew each other, it is quite likely that the match would be killed off at this early level.
How is that for a cogent argument? Life is never as simplistic as at first may seem.
On the other hand, I know firsthand of couples who tested late in the game, and this caused anguish -- not because of any negative outcome, but because of the somewhat implies message that would some problem surface, the chassan, or the kallah, would break off the marriage. Was there really love, if the match could be broken because of this? (Of course, they could still go through with the marriage, but know what potential disaster awaited, and take steps to prevent it. Even so, it causes emotional strains.)