It is a column of protein which, once damaged, really cannot be repaired.
Yes the products will say they heal damage, but that is bs. Maybe they have silicone which hides damage by filling in the porosity and making it seem smoother, or oils which can do the same thing... but the permanent damage is always there.
So.. Yes, permanent colour and bleach damage your hair and make it more porous. And YES you have to wait for the whole thing to grow out to get rid of that damage. ... though you can use products to help reduce further damage and make the hair look healthier.