freeze instance, not variable pointing to instance

freeze_var.rb

class FreezeTest
  def initialize(str)
    @text = str
  end
end

obj1 = FreezeTest.new("obj1")
obj2 = FreezeTest.new("obj2")
obj3 = obj1

obj1.freeze
p "obj1 frozen? => #{obj1.frozen?}"    # obj1 frozen? => true
p "obj2 frozen? => #{obj2.frozen?}"    # obj2 frozen? => false
p "obj3 frozen? => #{obj3.frozen?}"    # obj3 frozen? => true

obj1 = obj2
p "obj1 frozen? => #{obj1.frozen?}"    # obj1 frozen? => false
p "obj2 frozen? => #{obj2.frozen?}"    # obj2 frozen? => false
p "obj3 frozen? => #{obj3.frozen?}"    # obj3 frozen? => true