Apache is returning 404 when an invalid PHP script is called, even though  FallbackResource is configured and working fine for invalid scripts without the .php extension. 

Said another way, when I use FallbackResource, with a PHP file as the target, it works fine only when I don't reference an invalid PHP file. When I do, it doesn't work. I've spent hours poring over documentation and pounding on Google to no avail. 

### Configuration ### 
CentOS 6/64, stock install, all updates applied. 
Apache 2.4.6
php 5.4.16

Document root has a single PHP file "route.php" in it, with one line:  
<?php die("I was found"); 

/etc/httpd/conf.d/site.conf contains:
FallbackResource /route.php 

### Problem demonstrated ### 
When I go to 
I see "I was found". 

When I go to 
I see "I was found" 

When I go to 
I see 404 "Not Found The requested URL /invalid.php was not found on this server."

Wheat do I need to do to get FallbackResource to work for URLs that look like a PHP script?