It basically gives you a special case where being in a special type of half cover can grant you the ability to make a Dexterity (Stealth) check to hide. As soon as you leave that cover or that cover leaves you though you are discovered. The DM can however, at their option, allow you to leave the cover and make a Dexterity (Stealth) check to remain unseen. I think the skulker feat would allow you to do this same thing too - hide in a lightly obscured area of which half cover could be.
For the halfling trait to be better it might be better to allow them to hide in all instances of half cover and not just cover provided by another creature. At nothing else it is a weird trait. Nix it, I approve, instead give them proficiency in stealth. This would be more useful in many more circumstances.