I have some of those lower cost adapter options but just have not used them. I did dry fit them on my guns so I know they do operate. It makes sense if you can fit a particular flashlight in it with a rear button on/off switch. I happen to use the lights that fit the standard rails on common handguns. However, I also have tactical flashlights that will fit those lower cost flashlight adapters, so if some button batteries happen to die, or I want to try something different, I can insert my flashlight into that adapter then snap it into place.
A shotgun comes to mind. I normally keep my light within reach, but if I chose, I could readily pop that into place on a shotgun.
So to back up my other post, I say it just makes sense to have one or even more light mounting options. You plan out the scenarios and outfit your firearms as bright or as dark as you see fit. Mine are set. Some are bright, some dark, as well as alternate lighting available on the side to use or not use as needed.