Because the current behavior of `__method__` is equivalent to `__callee__`.

Example:

  # example.rb
  def src
    __send__(ARGV[0])
  end
  alias dst src
  %w[src dst].each {|n| puts "call #{n} => #{__send__(n).inspect}"}

  Ruby:

    $ ruby example.rb __method__
    call src => :src
    call dst => :src

    $ ruby example.rb __callee__
    call src => :src
    call dst => :dst

  mruby:

    $ mruby example.rb __method__
    call src => :src
    call dst => :dst