I’ve seen the same info as you, I think there’s some flexibility. Think about it this way, a seedling grown outdoors can get used to the power of the sun and that can easily be 50k-70k+ lux. The same thing happens with indoor lighting. A seedling that’s only ever seen 12,000 or 15,000 lux will be used to that level. But, if you took a seedling that was grown under lower power and put them under high power, they’d need a transition period. The real question is whether there’s a benefit to more. That’s much harder to pick apart. Since we move our plants outdoors, we think there’s benefit to the higher power as it makes hardening off practices a bit more successful.

It is electrically possible, yes. We put up a post today on our DIY grow lights and in that design, I designed that capability into the system using a potentiometer. The technical prerequisite is an LED driver that allows for variable output, which not all LED grow light drivers have. (It’s an extra cost item and not everyone will use it, so it’s often omitted.) While you could probably alter the high voltage output directly, LED’s are a bit complicated since they need a high voltage starting current to “fire up.” (So, I wouldn’t recommend it since the circuit design is complicated and would need timed gates to deal with differing current needs.) There might be commercial grow lights out there with this feature built in, but I’m not aware of any off the top of my head.

The “right” way to use these lights is to raise them up and get wider spread of the light. Yes, they are powerful, but that power is best used for covering larger footprints.