Holding the flashlight away from your body is one valid technique. However it isn't suitable in all situations. For example in the hallways of my own home, they arn't much wider than my shoulders, so there is no where to hold the flashlight away from my body. Another place it might not be a good idea is when firing a shotgun. Trying to hold and aim a shotgun with one hand/arm isn't easy. If it is a pump shotgun, the action is going to partially cycle when the gun is fired and you are going to then have to shut off the light to move the light toward the center of your body to run the action. If you remove the light from your adversary, you don't know what he is doing. You don't know if you hit him, you don't know if he is out of the fight, you don't know if he is moving, you don't know if there are more of them. If you leave the light on to run the action, then you might have well have held the light in one hand and the forend of the shotgun in the same hand to begin with. And if you pause to see what happened before you run the action while leaving the light on the target and away from your body, you are in trouble if you need to shoot again quickly.
If your opponent is using a good weapon mounted light, two things are going to occur at the same time. #1 When he points the weapon at you and turns on the light, you are going to be blinded. These lights are powerful, far more powerful than a standard two D-Cell flashlight. Your eyesight will be greatly diminished both from the powerful light and the fact that your eyes were adjusted to darkness. He will also be behind the "veil of light". In other words, you see a bright cone of light, but you don't know exactly where he is in that cone of light. #2 If you are being illuminated by a weapon mounted light, that means his gun is pointing at you; the second he sees you are a threat, he fires. He probably isn't going to give you time to accurately fire at that veil of light. "If I were in a situation and someone had a flashlight, that is right where I would aim." Of course if he was holding the light away from his body also, he would now know right where you were because of the muzzle flash and his flashlight and you still would not know where he was. It works both ways. If you were using a light, it wouldn't matter if he was holding his away from his body as much as if you didn't have a light.
Like any other low light technique, holding the light away from your body requires practice. First of all, can you shoot accurately with one hand. Secondly, you have to keep the light in front of your body at all times; otherwise you are clearly illuminating your own body. And, like any other technique, you need to know what you are going to do if you have to reload or clear a malfunction.
There are a number of accepted low light techniqes. They all have their good and bad points. They all have certain situations where they might be the one best technique for that particular situation. And likewise they all have their drawbacks. They all require practice not only to learn the technique but also to demonstate to yourself what you are capable of when using the technique. Most experts agree that there is no one best technique for all situations. They advise you to try them all and learn them all.
