The inverse square law would apply to this, although not in a straightforward way exactly. A brighter single light source will depreciate over a longer distance compared to a lower intensity single source. COBs although technically are a bunch of diodes, act more like a single source than a typical QB does. Of course it gets complicated due to LED light output overlap and such, and I'm not a physicist so can't really explain it.
Here's a link to inverse square law, which is the basic principle that the theory of COBs having better penetration rally around:
https://en.wikipedia.org/wiki/Inverse-square_law