Any porous surface area will be coated with beneficial bacteria. That's why sand beds are so much better than almost anything else. There is a lot of surface area. The same is true of coral rock (most BR/LR
was coral at one point). It is filled with crevices for water to flow through and bacteria to coat. So in that regard all BR will become LR
from a filtration standpoint. However it will not get that nice LR
look (coralline algea) unless it is seeded with coralline. That come from adding LR
that was recently harvested in the Ocean. You also hopefully get all sorts of beneficial (and occasionally not so beneficial) life along with the rock. All sort of critters and pods
and sponges, etc.