I haven't watched the entire episode online, just bits and pieces (I was in a hurry for work so I just picked random spots of the timeline just to get to the part of the accident). One random spot landed on the part where Saul is at the doctor's office as he discusses his health concerns. I do recall reading in the past that it is true that someone can be asymptomatic for years which is why they are part of the study group to locate the gene in hopes of 'turning off' that gene in symptomatic patients.
While the storyline was written specifically for Saul, an elderly gay male, I think the issue was "glossed" over for the viewers because they do not want to promote it solely as a GAY issue. As of now, HIV rates are now increasing in the over 50-elderly population, especially elderly women because they are not aware of STD and AIDS, and they are less likely to use protection. I think they were using that episode as an informative tool to reach those who may not be aware of the crisis affecting the elderly in regards to HIV and AIDS.
However, I was surprised that Saul was able to get the results over the phone! There's no way that would ever happen in reality! It probably was written for the sake of the show but I do agree that it is irresponsible.
I plan to watch the show in its entirety this morn.