I think - especially early on in someone's representative art journey - people often don't know what their goals are, or how to assess them. When you try to nudge people in one direction or another, sometimes it works! Sometimes they're just like, "augh no see, if it worked so well for so-and-so, the fact that it worked is what matters, not why or what the problem even was in the first place." I have a lot of empathy for that. People get desperate about improving.
In this case, even if "draw in pen, no erasing" doesn't align with someone's goals as a practice, it likely won't do any permanent damage. If, say, someone's problem is the opposite of what mine was, though - their work is super messy and incomprehensible in an uncool, unintentional kind of way, for example - I worry they're going to at least temporarily shoot themselves in the foot. Even a decade later, my sketches are way, way messier than they used to be. And I needed that! It's how I get life. It's how I get characters to move and emote. But, as you note, we all have different goals.
