These are DI (Direct Injection) engines compared to the older Port Injection engines. They produce less wasted heat, more energy is directed at physically moving the vehicle. As such they take longer time to get up to operating temperature. So if you need to drive short trips, ie less than 3-5miles good luck getting good MPG. This includes trips to drop the kids off at school, you grocery store, etc...So what do car makers do (Not just Subaru), they program the ECU to always keep revs up and keep them up longer. Look at what happened to Honda's Dream Engine with the oil dilution....the re-programmed their ECU to rev the engines higher and longer....to the behest of the Honda owners...
This is one of the reasons why all my diesel vehicles had an electronic heating element....If the vehicles depended on using coolant to warm up the cabin, good luck, I would be driving around with no heat for at least 30 minutes on a 45 minute commute....It is also why there's a company out there that sold a retrofit heater that you spliced into the cooling system, so you could pre-heat the coolant and the cabin before you drove off. There are YT videos showing snow and ice being melted while the vehicle is sitting in the driveway and the engine is NOT running...