The situation would be more like, there is a forced checkmate in 12 but it involves navigating a sharp position that is complex and any miscalculation could equalize the position.
On the other hand, you can simply exchange queens and rooks and have a clear winning endgame, but it will only result in a checkmate in 20 moves.
Almost any human would opt for the latter to avoid the risk. From the computer's perspective, there is no risk.
So no, I stand by my point that a specific choice of one of multiple possible checkmates is quite a poor indicator of using a computer to calculate moves.
> other than in end-game
This is frequently where such scenarios occur. Many end games are difficult for humans to play with absolute precision, even seemingly simple ones like knight and bishop vs. king. But when there are fewer pieces on the board is exactly when computers are able to perform incredibly deep calculations.
A good example is the notorious 30 move forced mate that Caruana "missed" in game 6 of his world championship match with Magnus, which occurred with only 3 pieces and 3 pawns left on the board.
However, I do look up a post-game analysis, and if there are some mid-game deep checkmates, they show up in it, and it is extremely rare. The example you cite about Caruana/Carlsen game actually quite falls into the category of what I referred to as 'endgame mates' - and looking at it with a potentially cheating player in mind, such cases are rather irrelevant: a cheater will win a game or arrive to an overwhelmingly better position in the endgame so such extreme measures with 30+ precise move checkmates will not be necessary.
[0]: https://en.wikipedia.org/wiki/Unified_Sports_Classification_...