Dude, we're busting your chops because you have misrepresented the adequacy of backups for the job they are called to do as backups in DIR cave/overhead diving.
If someone wants to skip bringing a primary (or doesn't even own one) and use a backup light for open water diving Hawaii that is fine. But that doesn't somehow imply that weaker lights are inadequate for caves. In fact weakers lights (like 10w HIDs) are surprisingly fine in caves but less than suitable in someplace like HI, Guam, or Cayman's where there's more ambient light.
If someone wants to skip bringing a primary (or doesn't even own one) and use a backup light for open water diving Hawaii that is fine. But that doesn't somehow imply that weaker lights are inadequate for caves. In fact weakers lights (like 10w HIDs) are surprisingly fine in caves but less than suitable in someplace like HI, Guam, or Cayman's where there's more ambient light.