Yes, agreed you can make a guess at torque and horsepower but it's unlikely to put the dynamometer people out of business. Presumably it uses a map of a similar engine airflow/fuel vs HP.
I don't see any load cells built into the engine mounts though !

 

But having your own personal dyno built into your dash is much more fun.

2 mins into this video shows the bhp/torque on my puny A3 TDI.

 

Very nice, I think I'd be having frequent accidents !