Heathrow Director is correct.
There is a holding side, a non holding side (protected side and non protected side) for a reason.
Sometimes that reason, for a non protected side, is air traffic.
Sometimes it is because there is a mountain.
I have a feeling, the children of the magenta line , really are like little monkeys , pull the handle and get the pellet. And they really haven't read up on the subject.
Visualization of holding patterns using either a paper chart or a directional gyro is actually an art and surely weeded many pilots out of the profession.