I teach Flap 3 then manage speed - you are only in selected speed until final flap. Fly managed after that.
For landing slats and flaps at zero, I teach select Vref + 60, then at 500 feet manage speed (Vref + 50). Works a treat.
There is nothing in FCOM about not using managed speeds for landing.
Well, there is actual a recommendation, PRO-ABN-10 P 12/22 and also in the QRH:
-Approach with selected speed is recommended.