Sorry for the delay, I was playing a little with ethereum mining.
This scene summarizes my tests:
1. Create a primitive plane over the floor. Difuse color 105 105 105
2. Removed the moon light from dome.
3. Change the right back lamp for a spotligh using rectangle area, height 200, width 400, lumens 400000
4. Removed the left back lamp and create a new "UG Box Light Rim":
Same config from others
On Surface: luminance to 40.000
On shaping: ScaleEmitter 34% Close top 50% Shallow flat 100% Shallow low 40% Straight sides -50%

If I was making the scene for first time, I would believe that this was the normal behavior but as I have the first picture rounded I'm breaking my head to understand how the light went square. Maybe something on render settings.
Still suspicious that some version change may have affected the product.
This scene is very small but I am using the same lamp post in several scenes
