That's so surprising I tried to find evidence of it online, but I couldn't. Partly because "index.php" is such a common thing that Google won't use it for a search term, which is ironic. Can you point to anything corroborating that?
There are a whole bunch of banned words. There used to be a whole slew of sites that indexed all of the things Microsoft wouldn't let you talk about. Here's an article about it in the Inquirer: http://www.theinquirer.net/inquirer/news/1041509/microsofts-...