Why is a single leg with your head outside the opponent's body prohibited (at white belt) in BJJ?

Question

In the IBJJF rules, performing a single leg while placing your head outside the opponent's body (as opposed to across their abdomen) is prohibited for juniors and adult white belt:

Single leg takedown while the attacking athlete has his head outside his opponents body.(**)
...
^{** Although it is a prohibited technique, the athlete will not be penalized.}

• Technical Fouls and Illegal Moves (ibjjf.com)

Other techniques which are prohibited at this level (such as wrist locks, body compressions, heel hooks etc) are due to them being potentially dangerous submissions, and reducing the chance of inexperienced competitors injuring eachother.

But I do not see the inherent danger in this type of single leg. Why is it also prohibited?

Answer 1

I haven't found a direct answer regarding why it is prohibited, but according to this Reddit post, apparently IBJJF rule 6.3.2 (actually 6.2.3) states:

IBJJF Rule 6.3.2 - Technical Foul: When the athlete who is defending a single leg takedown, while the athlete attacking has his head outside his opponents body, intentionally projects his attacker to the ground, by grabbing his opponents belt, to make him hit the floor with the head.

That suggests that they might be trying to guard against the danger of an opponent, accidentally or intentionally, doing the above, and causing a serious head or spinal injury to someone who is junior, or of lower rank, and doesn't know how to save themselves from the fall.

Side note, a further elbaoration in the rule book on the page you quote under 1.3.10:

• Whenever the situation depicted in picture 11 of item 6.2.3 (Single-leg with head on the outside) arises, by attempt to takedown or any other move coming from the ground, with the athletes on they knees or with a sweep motion, the referee shall act in the following way:
• For juveniles and younger divisions and white belts, the referee will stop the fight and restart the match with both athletes standing. No penalties will be given to either athlete.
• For the other divisions the referee shall not interfere with the match.