So there is no pass or fail of the TA I gather but isn't it written as if there is? That confuses me a bit (it needs careful wording which I haven't attempted to figure out).

The TA isn't the test case so it doesn't evaluate to anything. It just gives information to the test case about how it ought to be evaluated to fulfil spec requirements, say (or on the test based on the test case based on the TA).

Yet we have determined the beginning of rules to say something like that a postcondition or precondition which evaluates to false means the test should evaluate to 'not applicable'.