It hasn't been a 'qualifying' cross country for well over 20 years. The 100nm cross country flight is included in the mandatory 10 hours supervised solo flight time in the EASA PPL course. Once the organisation becomes an ATO, the training specification for this flight, like any other in the PPL course, should be detailed in Part 2 of the Training Manual and approved by the competent authority. It certainly will not be up to the whim of the individual instructor.