private_class_method confusion

mod_test_ffi.rb

require 'ffi'

module Process::Functions
  extend FFI::Library
  ffi_lib :kernel32
  attach_function :CloseHandle, [:ulong], :bool
  private_class_method :CloseHandle
end

module Process
  extend Process::Functions
  # private_class_method :CloseHandle # => This works as expected if here
end

p Process.respond_to?(:CloseHandle) # true?