ruby returns take blocks?

output.txt

mbj@mbj ~/devel/unparser (master*) % bundle exec ruby-parse return-a.rb return-b.rb
Using Parser::Ruby21 to parse 2 files.
(block
  (return
    (send nil :foo
      (send nil :arg)))
  (args
    (arg :bar)) nil)
(return
  (block
    (send nil :foo
      (send nil :arg))
    (args
      (arg :bar)) nil))

return-a.rb

return foo arg do |bar|
end

return-b.rb

return foo(arg) do |bar|
end

I expect both are parsed like return-b.rb.

In contrast RBX:

mbj@mbj ~/devel/unparser (master*) % ruby compile -S return-a.rb return-b.rb 
[:script,
 [:return,
  [:iter,
   [:call,
    nil,
    :foo,
    [:arglist, [:call, nil, :arg, nil], [:iter, [:args, :bar], [:nil]]]],
   [:args, :bar],
   [:nil]]]]
[:script,
 [:return,
  [:iter,
   [:call,
    nil,
    :foo,
    [:arglist, [:call, nil, :arg, nil], [:iter, [:args, :bar], [:nil]]]],
   [:args, :bar],
   [:nil]]]]