I mean, as insignificant as human peak condition is against Superman in the sense that it won't necessarily allow a human to deal direct death hits to Superman or to survive hits from him, being in peak human condition will still allow Batman to execute whatever stratagem he wants to execute faster and more efficient, so in that sense it makes sense for him to train and do all that crossfit shyt
Essentially, if you're going to go against Supes, you better off going at human peak rather than just show up flabby.
and Batman keep a kryptonite boulder in his utility belt for that basehead anyway