Hi @aslan_eyyup
The reason why CPU usage drops from 0.15% to 0.002% is because Simulink Coder optimizes the generated code. In this matter, when in PIL mode, if you terminate the model inside the PIL subsystem, the code corresponding to your model will not be generated and so the CPU has nothing to execute.
In the attached picture, you can see the differences between PIL subsystem generated code when using the output port and when using the terminator. When using the terminator, the code for the SOC Kalman Filter is not generated due to Simulink optimizations.

Hope this helps!
Regards,
Stefan.