The situation arose because as White I played very badly at the start of the game (and in another similar game). I was still relearning the game after all. I wanted to see if I could salvage a draw rather than be crushed to death.

I discovered that white can build a central fortress for the king. But this is not enough to draw if the rest of his pieces are surrounded and their mobility gradually reduced to zero. White would then lose because he'd either run out of moves or he'd be forced to making a losing move.

So I investigated what configurations of white pieces that could survive on the edge or in the corner and still have moves available due to an inner mobile piece. In the game with WhisperzQ I was able to do it because he didn't spot the possibility.

I agree with ughaibu that this strategem (which may have been previously undiscovered) adds complexity and depth. The central fortress is easy to set up but can prove useless in the face of a patient opponent. But the edge or corner mobile group is very hard to set up, and will be even harder now everyone knows about it!