H1b rfe with premium processing

My friend has applied for premium processing and he has received an RFE and a response was sent as well. It’s been more than 3 weeks but the case case status says RFE sent only till now. Does the premium processing apply as soon as it is sent to them or after the case status is updated as response received.

Also how long it can take for the status to update from RFE sent to Response received.

Time starts once they receive and actually open the packet.