Creaky hydraulic disc brakes on MTB
I think the shop was right - it’s just the pads moving around in the caliper. The creak occurs when the rotor is moving extremely slowly (like in this case), and the clunk is the sound of the pads hitting either end of the caliper AND whatever fork play you have AND whatever headset play you have. Try pulling on the brake really really hard and see if that makes a noise still.