oomis1105- My experience with Dor Yeshorim is limited to the two cases I personally know and one conversation with a frum doctor who is associated with Dor Yeshorim (I do not know what his title is or what his role is).
The first case I mentioned some time back in a different thread. A couple was about to get engaged but the Dor Yeshorim results came back positive for them for the same disease. They were told which disease it was and advised that there is a 4% chance of a false positive for both of them (hence a 7.84% chance that they are still compatible) and that they can take a 100% accurate test for $500. (They did and were not compatible.) I guess it’s possible that if there is no chance of a false positive by a particular disease they might not say which disease it is.
The second case was where a couple found out that they were carriers after they were married and were told to stay married. A relative, who knew he was not a carrier but his siblings possibly were, was told that it is Loshon Hora about his family to disclose it to anyone, including his wife. (She found out later but did not hold it against him since he was following his rov.)
A neighbor of ours received a letter from a geneticist which they thought said that their baby had one of the diseases that Dor Yeshorim tests for and they were both tested. They asked me to call a frum doctor who was associated with Dor Yeshorim and speak with him. (As it turns out- they both misread the letter, the letter actually stated that their baby did not have that genetic disease.) This doctor told me that the mission of Dor Yeshorim is not to make people “unmarriageable” but to prevent carriers from marrying each other. There are diseases where one parent being a carrier is enough to pass the disease to a child, but Dor Yeshorim doesn’t test for that since it renders the person unmarriageable.
Apparently they feel that one may be prevented from marrying if it becomes known that they are a carrier.