It's the reason you see so many complaints about passengers sitting with just emergency lighting, no plug sockets and no air con in summer if the driver forgets to disable it, even worse if the vehicle gets stuck in energy saving mode for the trip.
Nor sure what units you mean but just to clarify a few things about the 185s here...
The 110v DC battery output circuits on each vehicle are connected together, so lighting won't be affected if an engine is not running. Emergency lighting operates when there are no engines or no shore supply and the unit goes into a load-shedding state.
The plug socket supply is derived from the 400v AC 3-phase system so this won't be affected as contactors close to allow crossfeeding from an adjacent vehicle's alternator. Same goes for some of the equipment in the toilets (hand dryer etc).
The HVACs also run off the 400v AC 3-phase system. They do run when there's an engine not running but they operate in redundancy mode when being cross-fed, meaning only one cooling circuit per end of the saloon and only one third of roof heaters per end of the saloon (no bodyside convection heaters either), both modes run with supply air fans on low speed.
I don't know the driving policies or how often this is done but ECO mode can be disabled easily enough.