French language Q&A Forum

Hello - in the exercise it says:.....on a bu notre café sur la terrasse. 

Further down in the Q&A, White asked about the difference between 'sur la terrasse' and 'en  terrasse'. 

Céline's answer seems to suggest that the exercise above is incorrect. 

Have I understood correctly i.e. saying 'sur la terrasse' implies that something is actually physically on the terrace and so in effect, the extract should read: .... on a bu notre café en terrasse. ( One would assume that they were sitting on chairs on the terrace and not directly on the surface of the terrace as would be the case of a pot plant etc as per Céline's examples.)

If my understanding is correct, should the exercise not be corrected to say 'en terrasse' instead of 'sur la terrasse' ?