That doesn't mean that all your partners are as discriminating. While PIV sex is the least effective way to transmit HIV, let's imagine a scenario. Imagine this eatbeast got a drunk, normal sized dude in a bar and gave him the virus. He was drunk, he wasn't smart, and he's no shitlord. He's just horny and she's giving it away for free.  Now, imagine that a cute, fit, nice lady has a romp with that guy. Boom, possible infection. Maybe she's a victim of rape. Maybe she's got low self esteem and lets guys go bareback. Maybe that's her boyfriend and they go unprotected all the time because she thinks he's faithful and she's on the pill.  Now the infection is somewhere that you have a possibility of getting it. A cute, innocent woman of normal size. The kicker? Unless she got a STI test she has no idea. So she could possibly spread it to you, or to the general population of which you're a member.