I haven’t received any updates from nvidia.
But I got one clue from my experiments.
The m4000’s clock speed is slower than k2200’s.
773 MHz vs. 1046 MHz
(Referring to NVIDIA Quadro M4000 Specs | TechPowerUp GPU Database and NVIDIA Quadro K2200 Specs | TechPowerUp GPU Database)
The clock ratio is proportional to the approx. perf ratio.
so this seems Not-a-bug.