Way back when, in the 80s, I remember doing wax bullet training in low/no light conditions. This was pre-simunitions. Basically, you use revolvers, and make cookie cutter wax bullets with the empty brass and a fresh primer. It works really well, but only in revolvers.
Anyway, we would do this training in warehouses, motor pools and ship's cargo holds at night. We'd put on maybe one small light up in a corner, to cast some shadows and make low light channels and lanes among the vehicles, cargo boxes etc.
This was great heart thumping training. We are talking major intense fun. Wax bullets hurt like hell. You KNOW when you have been hit, for sure.
Anyway, we learned a lot doing this training. We tried one on one, two on one, teams, you name it.
But it always evolved into the guy who stayed hidden, and ambushed the searcher, won almost every time. If you stayed in a dark corner and waited, you'd get a back shot on the searcher just after he passed by.
Once this was learned, everybody would just hide, and the games basically ground to a halt. So we had to make rules to force action: everybody wanted to be the hider and not the searcher. We used time limits, such as, you only win if you get a kill shot in ten minutes, otherwise both sides are eliminated from moving up, or the hider automatically wins.
You make a scenario such as, "You and your partner are cops, and you have ten minutes to search and clear this warehouse." THen you switch roles with the other team, and compare results.
We had to do this forced role playing, because as I said, nobody wanted to search! Searchers got shot by ambushers most every time.
Now, here's the main lesson we learned, that I have never ever forgotten: Once the first shot was made, even by an ambusher on the searchers back after he passed by, it was very common for both parties to be shot in the resulting gun battle. The tiniest sound and shadow is magnified when your senses are keyed up for "battle." After the first "bang," your muzzle flash becomes a bullet magnet.
Forget about gun lights, I'm talking about just the muzzle flash, after the first shot is lit off. You'd take a great shot, and six wax bullets would be coming right back at you in a flash. Often, the first shooter would get "killed" by the guy he just shot.
The big lesson from this was: even if you have a perfect "kill shot" on your adversaries back, don't shoot until you can get cover. If you shoot from the open, even a great back shot from 15 feet away, you had better plan on a hail of bullets coming back at you. GET COVER FIRST if at all possible.
Also: Even if you totally dead bang bad guy #1, his unseen partner may shoot you, once you light off a round (or a flashlight for that matter.) GET AND USE COVER!!!!!
So the idea of entering a warehouse with a flashlight, even using it for a quick scan and off, does not appeal to me. Basically you are calling out, "Yoo hoo, Mr. Criminal, I'm coming! Take cover now, hide, and shoot me after I go by."
All that said, I would still use a light in my house to ID a bad guy, but I'd be VERY CAREFUL about tipping off a bad guy who may then hide and shoot me from cover.
Realistically, it makes the hide in the safe room and call 911 option sound pretty good. Assuming you don't have to go protect your kids and so on.
Remember: The gun light tactics are mainly for GROUPS of SWAT types, who lead with flash bang distraction devices. 5 or 6 LE raiders with lights would be terrifying. This is NOT so for a lone home owner at oh dark thirty.
As far as cops who strap on armor and a badge and a gun, and who by the nature of their job must frequently "clear" that warehouse after midnight.....well God bless em. That is a real gut check job I do not envy them doing.