"The template files are located in" shows child directory

I have a slightly weird little problem that I can’t figure out. I’m creating some child themes for a Multisite installation, and although they work fine, the text generated by themes.php that shows up in the admin panel is wrong. Here’s the header for my child theme’s style.css:

/*
Theme Name: THATCamp Twenty Ten
Theme URI: http://thatcamp.org/website
Description: A customized child theme for THATCamp based on the WordPress template theme Twenty Ten, by the WordPress team. Create your own custom 940 x 198 THATCamp header for this theme with the files at http://thatcamp.org/logos/.
Author: Amanda French
Author URI: http://thatcamp.org/author/amandafrench/
Template: twentyten
Version: 1.0
*/

The Twenty Ten theme is in the directory /twentyten, as you can see. The child theme, THATCamp Twenty Ten, is in the directory /thatcamp-twentyten-1.0. And here’s what it says on the Themes admin page:

The template files are located in /themes/thatcamp-twentyten-1.0. The stylesheet files are located in /themes/thatcamp-twentyten-1.0. THATCamp Twenty Ten uses templates from Twenty Ten. Changes made to the templates will affect both themes.

Why does it give the wrong location for the template files? Everything is specified correctly in the child theme, and the child theme works perfectly. Is it some kind of Multisite bug?