Do you have a reference for that in any Manual? Or it’s a company restriction/policy?
from FCTM-
PR-NP-SP-Green Operating Procedures-Descent Preparation
When landing performance permits, the best combination to reduce fuel costs and brakes oxidation is: CONF 3 + REV IDLE + Autobrake LO.
If the flight crew needs to reduce the landing distance, they should consider to use the deceleration devices in the following order:
- FLAPS FULL
- REV MAX
- Autobrake MED.
The flight crew should avoid the use of Autobrake MED in combination with CONF 3 and REV IDLE. This is because this configuration highly increases brake temperature and, as a result, brakes oxidation, which may be severe.