Hopefully the clarity and common sense applied, cleared up your confusion
And no, no one is claiming anything of the kind, as it relates to a "invasion proof border". That would be referred to as........drum roll........a deflection. The issues is that the further one's boundry is from one's population center, the better defended that population center becomes.
Think of it, this way, that even someone as uninformed in military doctrine & tactics, as even you appear to be, its harder to kill civilians when you're launching rockets miles upon miles away, vs few hundred yards. Its harder to kill civilians period when you're kept further away from them. Not to mention its easier to defend from higher positions, then from a low position. Its why you'd want to have look-out posts and defensive shooting positions up high, and now down at ground level