> Every chemical doesn't have to have a different connector. Maybe just ones that will cause a dangerous reaction if mixed.

The issue is that they're buying chemicals from vendors so they don't necessarily have control of what connectors are on the truck. If you have Bleach in connector A and acid in connector B, you better hope they don't send an acid truck with an A connector.

I think having a way to close the fill lines remotely would have at least seriously downgraded the problem.