For any multistep reaction there is a strong likelihood that "other enzymes" would make something that does not work for the next step (depends on the 3d shape

For any multistep reaction there is a strong likelihood that "other enzymes" would make something that does not work for the next step (depends on the 3d shape not fitting in the next enzyme). So at best some of the intermediary products for each organism with opposite chirality enzymes may not work in the other, at worst, it may be actively poisonous. Since time + competition breeds monopoly one would expect to see only one per competition zone (i.e. planet) given sufficient time. You could see both if there was an active breakdown mechanism developed in each that allowed minimally inefficient usage of the others resources (i.e. we see this on a macro level with things like lobster blood using copper instead of iron and being blue. We can still eat each other no problem without getting sick so there's no pressure to get rid of the one system)