The matter revolves around whether the Buddha touched upon every possible aspect of a main tenet or precept. This is impossible, even for a Buddha, all the more so given the ‘short’ 45-year Ministry.
My position is therefore in line with Lal’s “.. would not have anything significant missing.” In the sense that He may not have spoken about the case when one tells the truth regarding a particular matter, whether in its totality or partially, BUT with the intention of gaining personal advantage thereby, like politicians do. Truth is being applied in a devious way towards a selfish end. But the underlying mindset is an impure one. And it is this that counts, and THAT would not be overlooked by a Buddha.
y not