FLAG 4: ( 1010)
It is Black's choice to try hurting White's shape with the combination of , , , , , .
Concerning the number of ko-threats needed by Black to win a "late" ko, this sub-variation does not have any effect. Black still needs one external ko-threat.

FLAG 4a: ( 1011)
However, the position on the left side will change dramatically in the process, providing Black with the required external ko-threat, and withholding White her ko-threats in the top left corner. White cannot afford to start the ko "late" with this sub-variation any more.

FLAG 4b: ( 1017)
But White has the option of starting the ko "early", which she can choose successfully. Black needed three external ko-threats to win, but which he will be unable to get in the problem.