Will optimistic locking work for following code using updated_at attribute in update_all?

I want to use optimistic locking for Product model using updated_at. I have implemented the following code for the optimistic lock. There are other ways to implement optimistic locking like using lock_version. However, due to existing code restriction, I am not able to implement using lock_version.

  Product Model

  attr_writer :original_updated_at
  def original_updated_at
    @original_updated_at || updated_at
  end

  def stale_object?
    if self.updated_at > original_updated_at
      @original_updated_at = nil
      return true
    else
      return false
    end
  end

  def public_method
    ##code 
    result = nil
    begin
      result = private_method
      self.original_updated_at = self.updated_at
    rescue ActiveRecord::StaleObjectError => e
      errors.add(:base, ": Following records are changed while you were editing.")
      changes.except("updated_at").each do |name, values|
        errors.add(name, values)
      end
    rescue Exception => error
      ##code
    end
    result
  end



def private_method
    tries = 0
    begin
      raise ActiveRecord::StaleObjectError.new(self, "Product is changed while you were editing") if stale_object?
      attributes = #create hash using some code
      #some code

      attributes["updated_at"] = Time.now.utc
      Product.where(:id => self.id).update_all(attributes)
      self.original_updated_at = self.updated_at
    rescue ActiveRecord::StaleObjectError => e
      if tries < MAX_RETRIES
        tries += 1
        sleep(1 + tries)
        self.reload
        retry
      else
        raise ActiveRecord::StaleObjectError.new(self, "Product is changed while you were editing")
      end
    end
    attributes
  end