This is a basic rule and it is best to follow it rigorously. If you don't, the end could be fatal. As shown in this video where this man turns his back to a lion or a tiger, the felines' reactions are not long in coming. They jump to attack.
Indeed, these wild animals take this gesture as a lack of respect but especially make you an easy prey because taken by surprise.
TURNING YOUR BACK TO A TIGER CAN INSTANTLY TRIGGER ITS PREDATORY INSTINCT.
Even smaller prey can survive if they face the tiger instead of turning their back and running away.
All cats prefer to attack from behind. In fact, this rule applies to most predators because it is easier and less dangerous for a predator to make attacks from behind than from in front.
Unless there are special circumstances such as defending its offspring or the tiger's life is in danger. The tiger avoids frontal attacks.
In India, we know this only too well, so since 1986 forest workers wear a mask behind their head. The tiger, which is not known for its courage, instinctively avoids face to face attacks. Some tigers are easily intimidated.
It is formidable in ambushes from behind or from the side less front. One must face it and not run.