What i am asking is - Assume the road is evenly lit at exactly the minimum level
If we drop the brightness more down in all the road it will be "too dark"
If we drop the brightness more down in the parts between the poles it will be "too dark"
But what if we drop the brightness more down in the parts between the poles, but light a bit more under the poles, so that the overall power use is as initially ? This is indeed less than optimal, but for relatively small ratios between the 0L and 2L points, can't we "get over it" ?
Giving enough time to adopt, the overall brightness reduction will maintain better visibility. On many places I would even say less light would be better: Even with the imperfections (shadows from other objects,...), the car headlights would provide sufficient supplementary illumination, so you will see there without the glare from the brightly lit surroundings.
If you drop just the brightness between the poles, the brighter sections will just glare you and so the visibility on the darker section is reduced even when the level there is still higher than the case above.
By the way I have very bad personal experience with one type of very problematic lantern design: The light thrown just underneath the lantern came from just very small section of the lens. So small, the pole had made really dark shadow. The lantern was directed onto a small parking lot, so the shadow went in the road direction. And as the Murphy's laws go, there was deep pothole in the road was just in the place of the pole shadow, so I completely overlooked it. And it happened to be just in the way of my right wheel when going the "ideal path" (of course within my lane, it was slight curve), so I just hit the hole. At that time nothing appeared to be damaged, so I continued further. Then after few weeks (well, there was some negligence on my side to do thorough check after the hit) I just run on a road with some small bumps and the right front tire went flat at instant - at 90km/hour and in a road bend. I'm glad I managed to remain focused on what had happened and didn't do any stupidity like slamming the brakes or so... Well, I have found, hitting the hidden pothole had bend the rim, so the tire just held the air on just tiny corner of rubber. The uneven road then caused this corner to detach, so loosing all the air at once...
So even when small, the dark areas in lit background are extremely dangerous, even when the place appears to be lit well.
And by the way the lantern there was some HPS, it was at the time, when no one even considered LED's for road lighting. It was just wrongly installed (an overlooked pothole on the parking lot, where you move just the walking speed, will have less consequences than on the road, where you drive 50km/h)... And I would expect when that light would be of lower power, the pothole may appear at least when illuminated by the headlights. But because the level there was really high, the headlights had no power to overcome the glare from the brightness around that pole shadow.