I do not believe that Prime Minister May actually believed that the EU would work “constructively” on a parallel track to discuss how the UK would leave the EU AND to discuss a free trade agreement.
It ic called having your cake and eating it too.
From the EU side, the answer has arrived. Forget it. The leadership within continental Europe will extract as much pain as possible from the UK in the terms of leaving the EU BEFORE discussing future relationships. They have no choice. If they play nice, they risk other member states seeking the same deal – the benefits of membership without the costs.
Stay tuned on this one. It will draw out for some time.