I think that's a sign of them being VERY new to building.. less that they are teaching bad habits.
It takes practice to know exactly how much your going to need to cut off, and practice to cut the perfect amount of cotton.
I waste a lot because I can't yet gauge those things well.. in time I know ill be able to cut off the perfect amount, but I'm still wasting a lot because when I try to cut the right amount I'm shorting myself, and when I try not to short myself I waste .
So that is simply a sign of being new to building.
So really the question should be, should someone new to building be trying to teach building? I'd say no..
Trouble is, they are doing it as "guides".... if they showed proper technique that anyone with any sort of common sense know that you don't need 3 feet of wire and have to cut off those 10 inch (or more) from the post. I'd take one to two inches, but some are simply ridiculous.
When I started, I went and was using the Steam engine measurement and would give myself a bit of breathing room and even then, never got more than maybe an inch too much. In time, got a tester, I don't even measure lenght, I just use the "claws" as I pull my wire and go with the ohm range I want and again, give myself a bit extra for what I know I'll be cutting... If I waste over a total of 1 inch, it's be due that I usually snapped a leg while tightening in the post and have to undo a wrap to get what I need, which lowers my ohms by barely about 0.05 or so... nothing that I worry about as I aim for above 0.2 (and lately, I've been in the 0.4 to 0.8 range depending on wire.)
My cotton/wick, heck if I waste more than the end clippings of maybe 1 cm at the most now... if I end up with a large enough piece that's just unusable, I'll simply work it into a useable one, either adding more, or adding it to another strand... people tend to not realize that you can "comb" the fibers fairly easily.