jasmin287:
Does anyone know how else I can get this information, or why this M114 is not supported?
You need to study the GRBL documentation to get an answer to that question.
AFAIK GRBL only supports a subset of GCode commands.
You will probably get more information on a CNC forum or on the RepRap Forum where people are likely to be familiar with GRBL. This Arduino Forum is mainly for helping people write their own Arduino programs.
...R