In a fit auction, 4NT is always natural, unless bid in response to a conventional ask. As a jump, it has the same quantitative meaning as in a neutral auction. As a non-jump, it is simply to play, whether before or after the count.
This is especially useful with a minor agreed, when there may be a big temptation to settle for 3NT rather than explore for a tentative minor suit slam. This is particularly true in a pairs game, where five of a minor is unlikely to score well.
And sometimes 4NT will be a better scoring or safer spot than four of a major.