I'd say your mechanic didn't do the job right. While the Cruze is known for coolant loss, this much loss is a sign the repair job wasn't done properly.
Thank you. I've read somewhere sometimes it can take many days for the air bubbles to come out completely because im assuming he had to empty the system to do the work.... Maybe its just that? And he didn't bleed the system that's obvious with the fact he replaced fluid right after his work.Pic of the top of the reservoir looks normal.
Possible it has stabilized now; see if it continues to drop below that established level. Sniff around the engine compartment for any whiff of coolant on both a cold and hot engine.
The water pumps are known to leak when cold but *usually* stop when hot.