Question why task manager affect my cpu benchmark ?

[M2019]

i have a r5 2600 cpu i was benchmarking it using cpuz when i realized something weird if i do the benchmark while my taskmanager is opened i get higher results its not like a big margin :
single : 370
multicore : 3000
if task manager is opened i get : single = 380~390
multicore = 3100~3200
i did other cpu benchmarks and same results it feels like margin of error but why always higher while task manager is opened ?

 

[kerberos_20]

my rough guess would be timer resolution being low due to monitoring
try switching to high performance power profile