Wrong description in t3lib_extMgm::siteRelPath
this is not a bug. This is a hint regarding a wrong description of the method siteRelPath in t3lib_extMgm.
You wrote: "Useful for images and links from the frontend"
THIS IS WRONG!
siteRelPath does not respect config.absRelPrefix. And that is good. Don't change that! But please change the confusing description of that method to something like that:
"Useful for images and links from the backend"
"Only useful for internal processes within your extension."
Maybe you can add a hint HOW to use siteRelPath within the FE:
"If you need a valid path for your FE, then insert the result of this method into $this->cObj->fileResource($path)"