I would assume you need to wake the printer, but I am not sure to be honest.
Printers wake on a LAN because they are connected to via the PC, I'm not sure how Google sends the job.
I know on the AltaLink (Xerox) printers you can invoke it to look to Cloudprint for Jobs at the device in the Jobs app
so it is probably intentional. 6515/6510 is FujiXerox, I'm not sure how they would handle it. You may need to call Xerox and talk to 2nd level support