Intel BCLK Aware Adaptive Voltage is an option that enables the PCU to adapt the CPU voltage frequency curves to the actual BCLK frequency.
BCLK Aware Adaptive Voltage was introduced along with the Kaby Lake processors back in 2016.
To understand its function, you can refer to the Intel Adaptive Voltage Mode explanation. Whereas the Adaptive Voltage is designed to work with only the CPU ratios, when enabling BCLK Aware Adaptive Voltage, the processor scales its voltage calculations for all the V/f power domains and produces a voltage based on frequency as opposed to the multiplier.
The affected V/f power domains include the CPU cores, the Ring, and the integrated graphics (Slice and Unslice). The algorithm tracks BCLK at runtime and modifies voltage even when BCLK is changed at runtime at sub-MHz resolution.