Why are the BDSRADIO Urban National Airplay Charts different to the Billboard Urban Airplay Charts?

For Urban Airplay it says that Birthday Cake went #1 on Urban Radio on BDS Radio, but it only when #2 according to Billboard


Currently Diamonds by Rihanna is #31 on Billboard, but BDS Radio has Diamonds at #23 on Urban Airplay

Both sites claim to be powered by Neilsen, so why are they spilling different brands of tea?

Billboard uses AI. [/thread]

BDS Radio takes components from other formats (Urban, Urban AC and i *think* Rhythmic)... at the time, "Climax" was blocking BC because Climax's AI was greater than BC's.