The problem is not just getting a stuck or malfunctioning mag out using using alternative methods or just clearing the malfunction anyway you can. If you have received training from reputable places such as Thunder Ranch or Gunsite, you will perform malfunction drills and receive instruction on clearing theses malfunctions, that with repetition will form muscle memory to take over and you allow to clear a malfunction in a stressful situation such as a gun fight when rounds are headed your way. None of these drills that I am aware of involve poking a mag out through the ejection port.
Now for a gun that you only shoot at the range and not used for home defense or EDC, perhaps it doesn't matter. But you should shoot at the range and train as you are taught to reinforce muscle memory, otherwise what it the point. Which is why I always ask what is the point of these plugs. If you say it is to guide a mag in for a reload I would argue that these plugs just reduce the size of the funnel that you have at the bottom of the mag well. Just my two cents.