Not just GRBL, but CNC machines in general, see [ws680.nist.gov]. GCode was invented for CNC machines, then when 3D printers came along they adopted GCode too.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].