I think there's an error in the OSC Dictionary (https://www.etcconnect.com/WebDocs/Controls/EosFamilyOnlineHelp/en/Content/23_Show_Control/08_OSC/OSC_Dictionary.htm) specifically for macro commands.
Commands like /eos/get/macro/<index> indicate the index parameter is "Int, index of the macro list, 0-indexed" but it's not.
e.g. /eos/get/macro/0 and /eos/get/macro/1 only returned /eos/out/get/macro/0 (with no additional data) and /eos/out/get/macro/1.
The commands work as you would expect if called with the macro number itself (e.g. /eos/get/macro/803)