I am sure that someone of a higher level would be able to explain this better than myself, as I am only a double digit kyu, but my understanding of the problem and opinion is this :-
Theoretically, white is confined to the edge of the board and without any other stones on the board to run to, white should have a lack of liberties to enable escape. Preferably I would have liked to see black stones on B14 and F18, just to make the problem more obvious.
If white is unable to produce more ko threats than black can, black should be able to fill in at A19 and kill the white stones. I hope this helps.