4468, your post indicates that you have never flown into an airport with severe windshear, as can happen frequently. To have variable winds, not just gusting, means you can have a strong headwind suddenly become a strong tailwind, losing 40, 50kts or even more. That has nothing to do with certification or pressure altitudes. Start a go around from a bounce and have a 40kt airspeed loss from wind change and you are not going upwards, regardless of which engine spec or what weight you are.