There are a few problems with this idea. A forward position is much faster, both in terms of aerodynamics and the muscle groups involved with the pedal stroke.

There are a few problems with this idea. A forward position is much faster, both in terms of aerodynamics and the muscle groups involved with the pedal stroke. It allows even a relatively unfit cyclist to ride 20mph quite easily, rather than 13-14mph. This also means you can go further on a single ride. The purpose might be training, but you can't go very far on an upright bicycle—after 2 or 3 hours, there is quite a difference. Sitting upright puts more pressure on the sitbones. In a forward position, you can distribute the weight among the saddle, hands, and pedals. Again, this allows for longer, more productive rides.