In hindsight, we probbly should not have used team sport anologies for this.

But, for the last point, their skill level doesnt realy matter. if they arent trying to do it proffesionally its of no consiquence. If they want to compete proffesionally well, if they decided since school all the coaching etc would be provided especially if they get scooped up by a team earlier on.If not they would seek out such instruction. The base of information for a sport would be on average higher than not as people would literally practice doing said sport every day until they retire or decide to switch careers. Thats the issue with a sport analysis of this.
Now to apply this to self defence where (for sake of argument) the average amount of information would be lower? Would coming in with a base of information and some practice, even if it only builds your atributes be suffcient? More than likely. It would be the comparision of something over nothing.
Bad habits also seems subjective and based on your goals. A boxing coach can only relay what is bad for the sport of boxing, so fourth.
I dont deny its more individalistic, but thats not good or bad. Its based soley on the individuals abilities.