Sorry to jump in on this thread, and I’m not sure whether you discovered how to enable AWAY and HOME modes or just came up with a workaround, but I did run across a somewhat obscure Honeywell document with some Z-wave implementation details that states:
Basic V1 (basic set command implementation):
• Value 0x00 Device goes to Energy saving setting (AWAY mode)
• Values 0x01-0x63 and 0xFF Device goes to Comfort setting (HOME mode)
I assume that sending 0x00 will put the thermostat into an “eco heat” setting when it would normally be in heating mode and “eco cool” when it would be cooling.
It also details how AWAY/HOME states are reported. Sorry I’m too noob to upload it but here is the link to Honeywell’s site: T6 Pro Z-Wave Programmable Thermostat SUBMITTAL SHEET