The Sleep program mode is available in the driver I have been using that was ported over from ST. I set the ProgramMode to Home/Away/Sleep and ThermostatMode (Auto/Heat/Cool/Off) in webCoRE pistons based on time of day, Contact Sensors and Presence Sensor rules. Has been working for several months now. I will keep using that driver until the native driver can support it.
My use case is that I have my thermostats (2) set with a predetermined schedule for the ProgramModes based on Day of Week/Time of Day. This is set with the EcoBee app (or on the thermostat itself). Then based on contact sensors/presence sensor/Time of day, I set the ProgramMode (Home/Away/Sleep) and ThermostatMode (Auto/Heat/Cool/Off). For example .. If everyone leaves, the thermostats are set to Away ProgramMode. If someone returns, the thermostats 'resume' the scheduled program (usually Home). If someone opens a door or window and it remains open for five minutes, the affected thermostat is set to ThermostatMode 'Off.' When the contact is closed, the thermostat is returned to 'Auto.'
I can control the ThermostatMode with the new native integration. If the native driver can support ProgramMode, then I will be able to move to that driver exclusively and stop using the ported ST driver.