No, this misunderstands a basic distinction in Lojban between assertions and the rest and is just wrong for the function of words like {ai} and {ui}. There is a difference between being disingenuous and lying and that appears in the difference between saying {ui} and {mi gleki} when I am not happy: the first may be misleading but is not false (since not an assertion), the second is an assertion and is false. Mixing the two up, as people have been doing for 55 years in Logjam, is a basic logical mistake and the source of a large number of stupid arguments on the relevant lists (this may be one of them). The source is, of course, the English habit of not distinguishing the two verbally, one among many of the reasons for designing Logjam. I am unclear what a truth function that takes a person as an argument might be; typically they take a sentence in a particular frame, which does indeed contain the speaker as a relevant factor (the referent of "I", for example), but not a direct argument. to be sure, the adequacy condition on a truth function applied to "I am happy" requires that the referent of "I", the speaker, be in the class of happy persons, but that is a another matter. There is no truth function that takes {ui} as an argument, whether or not there is some function that takes the speaker as an argument.
{ai} is a harder case, because sometimes we rely peoples expressed intentions (not, it seems, on the intention to go, though one can build cases that are as significant as the intetion to give a million). Not fulfilling those expectations can cause very bad feeling, even, in certain cases, law suits or the like, or violence. But that does not mean that the _expression_ of the intention was a lie, even if it was misleading. It may not even be disingenuous, as xorxes points out, being what the speaker intended at the time, before he changed his mind -- or discovered that his fortune had disappeared or ... Promising to give someone the moon may be over the top or metaphorical, but it isn't false (nor true neither), at most it is insincere and unfulfillable (as of now, at least -- there is a treaty on that isn't there?) And, there are more ways to deceive than by lying.