These exercises are NOT for beginners and should be supervised by a coach who does them. This is just an example of long-term progressive build-up.
You may see fighters doing this kind of drill. In contact martial arts, it's important to strengthen your wrists for fighting and grappling. With submissions and holds, nothing sucks more than when you're sparring with someone and they have a crazy-strong grip. For striking, your wrists also need to be able to take impact as people don't tend to stand still when you're punching them. Dodgy punches happen.
Weightlifters who apply these same wrist-strengthening methods will significantly reduce their risk of injury and also increase the training they can endure. There's nothing that annoys me more than when someone can't complete sets of weights they should be fully capable of doing because their wrists can't take the pressure.
If you've really owned the passive wrist stretches https://www.t-nation.com/training/stronger-wrists-bigger-lifts and they feel easy to you, then it's time to step it up. First, test it from your knees. See if you can you support your weight in full wrist flexion. If there's no discomfort then attempt a push-up slowly. Again, only try a few and see how your wrists feel the next day.
Over time exercises like this won't become a big deal and you can just add them to a list of "things you can do." But the added benefit of having iron wrists will stay with you, and it's nice to take that for granted.