explicitly passed block argument is implicitly passed with super - ?

gistfile1.rb

class A
  def foo(a = 'foo', &b)
    puts a
    yield if block_given?
  end
end

class B < A
  def foo(a, &b)
    puts a
    yield if block_given?
    super()
  end
end

B.new.foo(1) { puts "boo" }

#=>
# 1
# boo
# foo
# boo