Several TV chefs including, the late Julia Child, have advised against pouring liquor directly from the bottle to a pan to be ignited, as 'flames could travel up the stream and ignite the bottle' causing damage, injury or death.
Are there documented cases of this happening or is this simply "lawyering up"?
Flame can travel up the stream, that is not news. There are many hospital admissions every year from people trying to add some meths (ethanol + methanol, "lighter fluid" in USA) direct from bottle to the BBQ to get it going properly
The problem occurs more often if the bottle has a wide opening, then you get easy flame transfer up the stream and into bottle. The expanding gases of the flame pushes out the rest of the fuel. Very ugly!
With a smaller bottle opening this effect is somewhat reduced (hence USA "lighter fluid" sold in squirt bottle), or using a "nip" pourer on a liquor bottle. But it is still a problem
Liquor is typically around 40% alcohol, so less violent, but still very hazardous. Do what chefs do, and pour out a measured amount into a small glass (they have to account for the cost too)
No. even if you had a high proof alcohol, with an open neck, and held your match to the neck of the bottle, the most you will get is a brief shoot of flame from the neck of the bottle. The path for the flame to enter the bottle also means that the flame isn't contained - which means no explosion (and alcohol isn't energetic enough to overcome that open neck). There is a risk that the very short burn could startle you into dropping and smashing the bottle - which is an obvious fire risk - but you are never going to explode the bottle.
See several YouTube videos where this is done deliberately (using pure alcohol) for a rocket effect: https://www.youtube.com/watch?v=a5RvwNBFMOY
