confusing output of method_added in 1.8 - not defined in 1.9

ri method_added.txt

> ruby -v
ruby 1.8.7 (2010-04-19 patchlevel 253) [x86_64-linux], MBARI 0x6770, Ruby Enterprise Edition 2010.02

> ri method_added
More than one method matched your request. You can refine
your search by asking for information on one of:

     Kernel::method_added, Kernel::method_added, Module#method_added,
     Numeric#singleton_method_added,
     Shell::CommandProcessor::method_added, Object::method_added,
     Object::method_added, Object::method_added,
     Object#singleton_method_added

> ri Kernel::method_added
More than one method matched your request. You can refine
your search by asking for information on one of:

     Kernel::method_added, Kernel::method_added

> ruby -v
ruby 1.9.2p0 (2010-08-18 revision 29036) [x86_64-linux]

> ri --list-doc-dirs
/home/deepak/.rvm/rubies/ruby-1.9.2-p0/share/ri/1.9.1/system
/home/deepak/.rvm/rubies/ruby-1.9.2-p0/share/ri/1.9.1/site
/home/deepak/.rdoc
/home/deepak/.rvm/gems/ruby-1.9.2-p0/doc/rake-0.8.7/ri
/home/deepak/.rvm/gems/ruby-1.9.2-p0@global/doc/bundler-1.0.0.rc.5/ri

> ri method_added
.method_added

(from ruby core)
Implementation from Module
------------------------------------------------------------------------------
  method_added(p1)

------------------------------------------------------------------------------

Not documented


(from ruby core)
Implementation from Shell::CommandProcessor
------------------------------------------------------------------------------
  method_added(id)

------------------------------------------------------------------------------


(from gem bundler-1.0.0.rc.5)
Implementation from Thor::Base::ClassMethods
------------------------------------------------------------------------------
  method_added(meth)

------------------------------------------------------------------------------

Fire this callback whenever a method is added. Added methods are tracked as
tasks by invoking the create_task method.