In LTSpice, for a 3-input logic gate system, the XOR gate isn't outputting what I'm expecting it to
Quote from the manual:

The exclusive XOR device has non-standard behavior when more than two inputs are used: The output is true only when exactly one of all inputs is true. Use the associative property of XOR's with multiple XOR devices to implement an XOR block with more than two inputs.

I won't bluntly say RTFM, but this should have been the first place to search for an answer, as opposed to posting a question online and waiting for an answer.