> If it’s known they don’t pursue and aren’t likely to attack you to secure an arrest, the risk for them from the person they’re stopping

If this is true and not just an assumption (FWIW, I think you're wrong - human nature is not that logical when in fight or flight brain) it should be possible to come up with numbers to back this up. There are many locations in the US where the default is not to chase.

As a side note, they have to detain someone while waiting. That someone's care is also legally in their hands at that point; it doesn't make a lot of sense from a civilian safety perspective to just set them on the side of the highway.