What?.
A transistor is not an AND gate, that would be two transistors.. And an inverter is a transistor with a resistor. Anyway, that's one level of abstraction deeper than gates and this sim does not touch that *at all*?.
The fact that all other gates (and thus, all possible logic too) can be built from NAND makes it more or less fundamental, cuts off unnecessary entities. And it's not even a unique propery of NAND, lol