Let $P,Q$ be two distributions on a finite set $X$. Consider the following metric* ​$$ d(P,Q) = \frac12\max_{A\subseteq X} ||P​(\cdot|A)-Q(\cdot|A)||_1. $$ Obviously, the total variation metric $\frac12||P-Q||_1$ is majorized by $d(P,Q)$.

Question: has anyone encountered $d(P,Q)$ in the literature? Does it have a name?

*It's not immediately obvious that $d$ satisfies the triangle inequality, but I think this can be shown.