Vega memory underclocking

[tildearrow]

It seems it is impossible to lower the memory clock on Vega:

# echo manual > power_dpm_force_performance_level
# cat pp_dpm_mclk
0: 167Mhz
1: 500Mhz
2: 800Mhz
3: 945Mhz *
# echo 0 > pp_dpm_mclk
# cat pp_dpm_mclk
0: 167Mhz
1: 500Mhz
2: 800Mhz
3: 945Mhz *

Am I doing something wrong or is this a driver bug?