I purchased a 2013 Subaru Crosstrek XV (MT) and installed a base plate for dinghy use. I have towed it successfully for several hundred miles without any problems. This vehicle was listed in the 2013, 2014, and 2015 MotorHome Guide to Dinghy Towing as being suitable for towing behind a motorhome with all wheels on the ground.
Since the Crosstrek was not listed in the 2016 dinghy guide, I contacted the dealership from which I purchased the vehicle for clarification. I reminded them that, when I bought the Crosstrek, I indicated that I was going to use it as a motorhome dinghy. I did not receive any advice against using it for that purpose at that time.
In response to my inquiry, I received two calls from the dealership (one from the service manager). I was informed that Subaru Motors had been contacted and they confirmed that the 2013 Crosstrek is suitable for dinghy towing as per the operator's manual instructions, i.e., no speed/distance limitations when towing with the parking brake released, the transmission in neutral, and the ignition set to the ACC position.
I asked why the Subaru's were not included in the 2016 guide. They had no explanation. Assuming nothing related to towing has changed from the earlier models, why is dinghy use now verboten with the 2016 models? As lryro9301 suggests, it is most likely some kind of legal CYA maneuver. I wouldn't give up on using your Forester as a dinghy without further investigation.