yes it is

I use many times the security check on the 2nd floor of the C terminal and walk back to B gates. Also important to visit the atlantic lounge if flying U2 with Priority pass or BA as Sapphire (both use the same contract lounge) depending on your departure gate

Also note that B security tends to be busy if an EK 380 and EY/ QR depart at the same time so C gates security should always save you time