Either way, I know that if you'd asked me four issues ago what we might end up seeing in future issues of this title, the last thing I'd answer would be topping-from-the-bottom.
In a way, it's how the story started, albeit that as far as we know Laura didn't know about the real effect of the lotion then. But my reading is that she was the one who wanted Kurt's (nice name) cock to be bigger in the first place. And that
might be her only motivation here. Rob's cock won't feel as big as Kurt's
feels, and she knows a way to fix that. Has it been made clear that she understands that the lotion is responsible for what's happening? I know that in issue 10 she asks Kurt what's going on, and says it didn't use to be like this, but she doesn't mention the lotion. He kills that conversation by getting his cock out, and even telling her to get the lotion. But though she feels the effect, she doesn't show any sign of making the connection. I can't recall it being made clearer later, but I could be forgetting something.
One of the things I like about this comic is that it's all (apparently) accidental, and everyone's a victim. The lotion initially made Kurt horny (and Laura too) and then he discovered that he could satisfy his desires. But they're never really satisfied - hence his nocturnal adventures. I think he says at some point that he's hard all the time now. His self-control has been eroded by the lotion as much as that of the women.