Confused by documentation for /alias/

[graq]

Hi

From: http://wiki.nginx.org/HttpCoreModule

__BEGIN__
For example:

location ~ ^/download/(.*)$ {
  alias /home/website/files/$1;
}
The request "/download/book.pdf" will return the file
"/home/website/files/book.pdf". Note again that only part of the request
URI after the location is appended to the path defined by alias.
___END___

Why doesn't this return the directory "home/website/files/book.pdf/" ?

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,213617,213617#msg-213617