@dd_snaplogic - If you can find a case where this is working the way you originally described, I would be very interested. The snap always uses an equality join, so “left path value == right path value” is the only way this snap works. By adding the not operator (!) to either of the values would simply make it a boolean value meaning that it evaluates as true only when the incoming value is null, zero, or empty string.
I’m checking with our developers, but perhaps the snap’s datatype checking has been improved so that it is now throwing the error that boolean is not comparable to a string value. But the evaluation still would not have been the behavior that I believe you were intending. (i.e. “true” == “abc” )
