Sure.
But in ascending to this higher tier of understanding, a different set of rules now applies, ones that were irrelevant or inapplicable before--a new rendering of the highest-tier abstractions. In any tier, the GM must play fair. That doesn't mean they need to play kindly or coddlingly or positively--but there needs to be restraint of some kind, or it simply collapses into arbitrary action. You can quite easily have a bloody PC-abattoir of a campaign, a grimdark "meditation" on how everyone always sucks all the time forever, a one-mistake-and-you-die two-mistakes-and-you-suffer-fates-worse-than-death, or whatever else in your campaign. But if you as GM don't have some kind of limitation under the maximally-abstract umbrella of "playing fair", you've broken something terribly important.
When one ascends from "play only what is predetermined" to "break from what is predetermined when needed", the new restraint that applies is some variation of, "But only do so when you make it legitimately possible for the players to know." That doesn't mean you have to tell them right away. It doesn't mean you have to "tell" them at all. But they need to have a true, legitimate, fair shot at actually discovering how/why/what/etc. Without that limitation, you just have the GM doing whatever, whenever, because you've created an exception without closure.
And I really do mean "ascending" here. One lays down a basis of thought and explores its space, and then ascends past the bad parts of the old limitations by understanding that there may be a more nuanced, better-fitting limitation which evades places where the old limitation went astray. But there are some limitations induced purely by the medium--and the fact that the GM is the sole source of information is why many of those limitations apply.
