A readback does no harm provided the RTF isn't too busy.
I've heard controllers at some 'busy' positions (usually training films made in the USA) who pass a stream of instructions to multiple aircraft wthout a break and after each aircraft specific instruction they say 'ident to acknowledge'.
What I meant to say was OK it's a 'mandatory' in '413, but no-one minds if it's not read back provided thay see an ident appear on the label of the aircraft they have addressed.
Last edited by chevvron; 21st Feb 2018 at 15:43.