Good point.

Still, we have highly-effective sensors in other parts of our bodies, further away from the brain, and surely we could drop that check somewhere else. At least when it comes to eyes, one can make the argument that they should enable split-second reactions to run from that predator as soon as you spot it, so they should be as close as possible to the mainframe... whereas nobody is going to die if they can only smell wolf poo a second later.

Seems like smelling something toxic a second before consuming it would be useful as well.

>whereas nobody is going to die if they can only smell wolf poo a second later.

I'm still alive today because I can detect smoke very early. This ability has saved me from indoor electrical fires and wildfires. Hunter gatherers who lived in makeshift shelters probably depended even more frequently on this ability.

Would detecting the smoke 1 second later have made the difference? (I think that's the essence of GP's comment.)

Signals can travel relatively fast across the entire length of a human central nervous system. Proximity to the brain likely benefits signal-to-noise ratio more than speed.