(;B[bs]C[10.000 year ko. Neither player wants to start it as that means needing an extra threat. In the end, if there are no threats left, White cannot connect it, but Black can, making it seki.
Even though Black may need an extra threat to win it, White's threat needs to be as big as the group while Blacks threats only need to be worth more than making it seki. Black has a lot to win and little to lose by making it ko.RIGHT])
(;B[cr]C[White is alive with points.]))
(;B[bs];W[cs]C[Gote seki (you still need B2). You could have killed with ko.])
(;B[bs]C[Gote seki. You could have killed with ko.])
(;B[cr];W[br];B[cs]C[White is alive with points.])