Tornado warnings are sudden, the last thing you want to do is put everyone in their car and on the road during a tornado warning. A tornado watch is not reason enough to shut down. A tornado watch means “keep an eye on the weather”. There’s a lot of room between watch and warning (there’s also “tornado emergency” in extreme scenarios) and deciding when things are bad enough to close but not bad enough to shelter in place is more of an art than science. I’m sure whoever was in charge of keeping the warehouse open or closing it down isn’t exactly sleeping well.

I can’t answer your question exactly but I have been in a warehouse when a tornado warning was issued and the warehouse in the path of the storm. They got everyone together and put us all against the strongest wall furthest from the approaching tornado. (It lifted before reaching us)