I thought that at first, but it is not the case. It does not seem to be an error in the documentation although there are a bunch. They aren't even listed among the all the aesthetics, in [aes.r](https://github.com/hadley/ggplot2/blob/master/R/aes.r#L7)

They are just like any other parameter. However, for `geom_vline` and `geom_hline` the `xintercept` and `yintercept` are parameters  but they are listed in `aes.r` as part of all aesthetics.

So whatever is and is not listed as an aesthetic is immaterial, the code maps both.