There is nothing wrong with raising / lowering the main on the mooring. It can be more relaxed and there are more hands to help. The key "ENSURE THE MAINSHEET IS EASED AND THE SAIL IS LUFFING." Otherwise you may start sailing on the mooring.
ISPA Yachtmaster Offshore Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203, 204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)