There are a lot of conspiracy theories about AIDS, and in the case like the death of Steve Jobs I guess this sort of rumor is bolstered by the fact that a lot of people hid their diagnosis due to stigma. Jobs was famously very focused on image. But I think most of that stigma was gone by 2010.
The stigma is most definitely not gone with the exception of the gay community, and maybe younger folks. If Jobs had AIDS and hid it, it wouldn't be a shock, but I think it would be a contributing factor to disinformation as most people believe the pancreatic cancer happened on its own and was exacerbated by his alternate treatments.
Well the other thing is, if he got a positive test in 2006, he'd be on anti-retrovirals and wouldn't have died of it. He had money and access to good doctors. It's rare for someone like him to die of AIDS complications.
https://wikileaks.org/wiki/Steve_Jobs_purported_HIV_medical_...
Conclusion is that the documents shouldn't be taken at face value... so maybe not?
However, if he was HIV+ I can totally see why it would be covered up.
I guess it's a big question mark, but it's not unbelievable.