I can't help but notice the limitations of that study namely:
The researchers noted that their analysis has several limitations. It did not (1) include same-sex couples, (2) discriminate between vaginal and anal sex, (3) establish how often couples had sex, (4) establish the direction of HIV transmission, (4) establish the exact viral load at the time of transmission, (5) account for sexually transmitted infections, or (6) determine the extent of condom use.
does not include, same sex, frequency of, type of sex seems rather important limitations especially as any one of them could dramatically effect any results, I just wonder how relevant such findings are without including more data to include these limitation or you end up with a very narrow result.