On some of the Passats and/or Jettas I had between 2000 and 2014, water used to regularly collect in a trench behind a bulkhead at the rear of the engine compartment. This was maybe about 6-8 inches in front of the main cabin bulkhead and was where fresh air entered for the heating and ventilation system so was open to water from the windscreen. There were drain holes with rubber pipes at the bottom but these often got blocked with leaves etc. I don't think any of the water ever got into the passenger cabin though.Could it possibly be coming through when the water goes down the drainage hole below the windscreen? Thanks
The design of the T-Roc is different and I can't see any equivalent trench, although that may be under the large plastic apron at the rear of the engine compartment, so I would say it is not impossible for water to build up and leak into the cabin. It would be worth raising this with the workshop to get their view.