Currently there is only the visual given by the hips to show how wide stretch the girl, and how much of a gape you cause in the aftermath. I spent a long time at the start of the game's development debating on how I should organize their reactions and ultimately it boiled down to not wanting to be bogged down with having too much devtime.
This is especially true with writing, each variation would need its own line of dialogue, exponentially. So if there are 9 inches, to work with in length, each inch would need 9 inches of girth to go along with it. Unless ya just want some basic acknowledgements on the girth, the required load even if dumbed down to "small, medium, large etc" would be too great for right now.
If I can find out how to reasonably change the image of the penis with image transforms then I can see that being done, but for now, especially with text, it will remain with length being the primary determinant.
All this being said it is worth noting that the VOLUME of your cock IS taken into account for things like condoms, and I could reasonably see using that as the basis instead of a rounded version of the cock length. I dunno, we're still really early in development, and Im kinda dumbass, so we will have to see.