Perfectly normal if there's a slight 'tick' or 'clicking' sound. The clearance between the cam lobe and tappet is a little greater than normal, and this exercise simply helps the new parts to seat/wear in with the old parts without putting too much stress on either. More precautionary than mandatory for the local engineers. For myself, I like the sound of valves talking away on a cold engine. Only helps to know they're breathing freely.
Just pay the mechanic another visit after running in a couple hundred kilometers. Appropriately a 'recognized' mechanic would be expected of telling you to do just that.