True and False are specific claims. Up and Down are also specific. Something and nothing are specific.
Null is the unknown. In a logic truth table you will see values of true, false and null. Null is not nothing, it is that a value is not known. In computers, if a string variable is null, that means has no value. Use the idea of the field for someone's middle initial. The field is blank when someone submits it. Does that mean they have no middle initial or they just did not type it in. Having a null value in a middle initial cannot claim that the person does not have a middle name or initial, just that we do not yet know. In some systems people will use symbols like "#" or "*" to indicate that they do not have a middle name or initial. Now we have specific information. We can say affirmatively they have nothing for a middle initial or name.
Null is actually the biggest container. It holds both something and nothing. It holds anything and everything. It is the largest container and the smallest container. It can hold universes, sub atomic particle ideas or a vague cloudy thought.
Nothing is not null. Nothing is a specific state. A known state, not an unknown. In some computer languages it can be difficult to tell if a variable does not have a specific value. To know if it is "empty" (a known value) or "null" (unknown or never/not yet assigned).
Null Theism or PNT is not about belief in nothing. It is quite the opposite. It is belief in the unknown. Science loves the unknown. Learning, exploring, growing.