I am leaning towards not second guessing the Buddha.
We don't know what would of happened, so saying there was a lie, or saying it wouldn't of happened and was only a skilful means is only adding onto what is there, the fact is we don't know about that.
I agree it was a skilful means of persuading him to practice, but more than that is unsupported guesswork and addition, because we do not know the range of the Tathagatas power, but we do know Nanda was comparable in beauty to the Buddha and mistaken for the Buddha at least once, if memory serves, and being enlightened quite a catch for any dove footed nymph, if you ask me so would the Buddha of had to do anything? not really, but I don't actually know, it is just unsupported speculation & addition.
and the Buddha wouldn't lie (AN 9.7) so saying something which is non-factual would be covered there as it is a statement designed to mislead someone about something, whether in a positive direction or not.
He who knows only his own side of the case knows little of that. His reasons may be good, and no one may have been able to refute them.
But if he is equally unable to refute the reasons on the opposite side, if he does not so much as know what they are, he has no ground for preferring either opinion …
He must be able to hear them from persons who actually believe them … he must know them in their most plausible and persuasive form.