No I am not confused and neither are all the others that farm and has used Roundup for years. Roundup is one tool. It is not the best tool in many situations. It is highly ineffective in many. That is why seed companies are getting far away from it by adding better genetics to allow better tool.. You mention a pre-emergence. Well that is tough and quite funny as the example I referenced was an actively growing alfalfa field. Just how do you treat that with a pre-emergence? The regrowth is not from seed it is from the root system that Glyphosate failed to kill.Perhaps you are confusing Reward Herbicide, or several other like them. Anything with Diquat as the active ingredient will perform that way, and their labels clearly state that.
Liberty herbicide will do the same thing in my very limited experience. It never mentions the word "systemic" but it does claim to control perennials.
Now it is getting way off subject so I will attempt to bring it back. The thread was about killing mature stumps that are sprouting immature sprouts. You and others talk about hw effective Glyphosate is for the task. How many commerically available "brush killers" use Glyphosate as their primary ingredient versus 2-4-D, Picloram, Triclopyr, or Imazapyr? I would really like to know.