I see /beg/s all the time who try to draw everything in 1 line, don't erase, and then beat themselves up over it when their drawings look like shit.
People need to understand that the whole "draw everything in 1 line" and "only use pen" and "don't ever erase anything" stuff is just for the course, once you're done with the course, you can do things your own way again.
Even pro artists don't draw everything in 1 line or never erase. That's silly and puts unrealistic expectations in the mind of true /beg/s who just started out learning.
You'll only lose confidence and will start to hate drawing in general if you take Peter Han's teachings too far.
The drawabox guy is a good example for this, he is literally teaching others how to draw while his art looks like shit.
It's because he just blindly copied Peter Han's methods and how he draws instead of figuring out what works for him.
You should take the course, but really only focus on the exercises, all the extra rules and stuff that he tells you is just bogus that will only limit you in the end.