Dear Obi.
The speEd of controlling the bleedflow in a compressor is not measureable, this is controlled by the fadec/eec, depending on rotorspeed ,temperature and thrustsetting.
The manufacture develops a special program, and during development of an engine, several test will be done to figure out the optimum on rotorspool and blade position control.
To reduce load on an compressor to avoid a stall, the engine is every time controlled via temp and pressure sensors, when the VBV/VSV are not operating correct, bleedvalves open, to remove the air from the compressor. There is no abrupt change in movement, everything is smooth an in relation to avoid stall/surge
rgds