It is standard operating procedure at Lufthansa to do the readback starting with the callsign. The reason ist the following:
It gives the PF time to set the new HDG/Alt. etc. in the FCU, and then the PNF does the readback directly from the FMA (and by that checks the new setting on the FMA), thus making sure that the PF indeed made the correct settings. It is therefore another way to check the correct entry/setting of the clearance.
By the way, the
search funtion is your friend
as this subject has been discussed
several times already on pprune, e.g.
here
Merry XMas,
DBate