I doubt every chemical facility uses the same style connector, so at some point in time this information would have had to be communicated to the chemical suppl

I doubt every chemical facility uses the same style connector, so at some point in time this information would have had to be communicated to the chemical supplier anyway. And sure, the supplier could just happen to send the truck with the exact right connector for the other chemical (though that wouldn't be a problem if they just moved the inlets apart), but that's a lot less likely than a screw up when the connectors are the same. I'm not saying (and I doubt the CSB is either) that any of this would eliminate the possibility of incidents. The point is that they'd become much less likely.