Thanks Dwight. I'd actually tried changing that value and it simply made a small square of light on the floor smaller and less intense. Where you are the expert on this stuff and your solution behaved weirdly, the solution suggested itself for me.
This file was created in AC 9 and had been opened on and off since then. This was the first time it had been opened in AC 13 and it was behaving strangely. Parameters just weren't behaving the way I'd expect. These lights had originally been set at the defaults, raised 2 feet higher and the intensity value was dialed down. There was very little fuss involved.
Figuring something may have changed in these objects along the way, I selected all of them, switched to a different fixture type and then back. This set the fixture back to the defaults. I raised it 2 feet and took a look. All was well again and I was getting relatively even lighting. I just tweaked the falloff up a bit higher. Now I need to tweak the settings a bit and throw in some general light bombs to illuminated the ceiling.
So for whatever reason these objects seem to have changed in their behavior and didn't behave the same way in 13 as earlier. Your suggesting something I'd also tried and it not working told me I was in a bizzaro universe and it was time to start from scratch. Thanks.
Jim