I’m not sure that leaving a piece of walnut in a locker would cause any issues, but yeah, it probably would be a bad idea to sand it at the co-working tables for a number of reasons. That would apply to every kind of wood, whether it is on the list or not. Taking reasonable precautions to avoid causing foreseeable harm to others is good policy, but taking extraordinary steps to avoid extremely unlikely issues isn’t. If someone is so susceptible to a reaction that they’d get sick from being in the same area as a piece of walnut furniture, hanging out in a building with a wood shop is a really bad idea in the first place.
In other words, if you’re highly allergic to peanuts, don’t go to Texas Roadhouse.