Will the OC be testing the strengths of cylinders submitted based on when the first cracks appear or when the cylinder is completely crushed?
As indicated in the quoted clause, the testing will be done in accordance with CSA A23.2-9C (Compressive Strength of Cylindrical Concrete Specimens). That standard describes the details on how the compression tests will be performed.
To save you a bit of trouble, clause 7.4 of said document (specifically CSA A23.2-9C) states something along the lines of “The load should be increased until the specimen fails (i.e. shows visible cracks).”