Height loss above 20,000 ft in a stall recovery (or avoidance) is not an issue that is worried about. If you are 20,000ft above the MSA then where is the problem in using some gravity to assist a prompt and effective recovery.
If the recovery is made correctly, then as you say, no problem. But if in IMC and particularly at night, the sticker shaker operating suddenly will almost certainly be an unexpected event catching a crew by surprise. It would then take only a few harsh control movements to cause serious overcontrolling and unless the pilot was on the ball with his basic instrument flying skill, an unusual atttitude can result. Now you have a deadly serious problem while in IMC. Realistic unusual attitude recovery training is rarely conducted in airline recurrency training. It is seen as unnecessary and a waste of simulator time. Even if this training is conducted it might only be once every couple of years. Not exactly effective recurrency.