Strange Behavior in Flex Builder 3

I've noticed that at least in my copy of Flex Builder 3, the code-completion feature doesn't seem to work entirely correctly. I was trying to define a variable of type ListBaseContentHolder, but typing the dot "." after listClasses brought up a list of available classes -- but not ListBaseContentHolder!

var lb:mx.controls.listClasses.

All the online documentation said it was there, but Flex Builder wouldn't show it. I typed it in manually,

var lb:mx.controls.listClasses.ListBaseContentHolder;

and it compiled just fine. What's going on here?

Update, 9/30/2008: Apparently, by design, the folks at Adobe don't want you accessing some of the more arcane classes. Not sure why -- this is not arcane; I've been using it to get my work done :-)