Lal,
-‘If a bhikkhu untruthfully declares a high-achievement (i.e., magga phala or jhana), he commits an offense’-
That makes sense.
You will appreciate that I, and many others, cannot go into the original Pali to extract the true meaning in this way. So where the English translation seems at odds with established fundamental concepts in Buddhadhamma, I tend to go (until the matter is eventually resolved, like here) by whether it would follow from those established concepts or not.
In the case cited by puthujjana, it is all too easy to accept that the bhikkhus did not lie to those lay people, i,e.that they indeed had those supranormal powers, and that their wrongdoing consisted only of having declared them for selfish ends, because surely Bhikkhus should be aware of the consequences of lying about their attainments even when no Vinaya rule is in place. Which brings up another point:
Does the fact that they lied mean that those Bhikkhus had not attained any magga phala? Or, conversely, are Ariyas incapable even of such a thing? …worse, of claiming, for instance, a higher magga phala than they know to have actually attained? Are they prevented in the same definitive way as are Sotapannas, for example, prevented from committing papa kamma leading to the apayas? On the surface it is just a lie, but the claimant is thereby getting additional undeserved respect, a subtle kind of theft to add to the inflated sense of ego.
It may be that you have touched upon this point in a post or in a reply to a question somewhere already. I am not sure.
As ever, with infinite Gratitude