For myself, I tend to believe in the totality of the play. Which is to say that if you do not play the bad guys to the hilt, then the players will start to believe that they are invulnerable; they will no longer play realistically. They will no longer enter encounters cautiously.
They will no longer do basic things like have spells, abilities, or magic items that allow them to escape encounters, instead concentrating solely on offensive firepower.
On the other hand, if you play the encounters to the hilt, it will only take the unwary one time to understand that all of those "disused" items and spells and abilities (or even choosing not to engage in combat on occasion) really do have importance.
TLDR; the DM must be Cobra Kai. SWEEP THE LEG. NO MERCY.
I think this comes down to Combat As War vs Combat As Sport. And it should really be Campaign As War vs Campaign As Sport, since I've never known a GM who ran Combat As War but Exploration As Sport (or visa versa). Typically, IME, a campaign falls somewhere on the spectrum between War and Sport, rather than at an extreme.
In "pure" CAW, there is an expectation of unfairness (or at least asymmetry) on both sides, and therefore anything goes. (Obviously, this does not generally extend outside of the game world - if the players are fudging rolls, you probably have something else going on.) It's expected that the GM may put challenges in the path of the players to which the characters have no viable solution. It's expected that the players may come up with unanticipated solutions to those "impossible" problems, and that the only fairness they expect is that the GM won't use fiat to render those solutions unfeasible, but rather play them out to a reasonable conclusion. For example, a low level party might come across a massive horde of orcs camped in a forest. They have effectively no chance of success if they take the orcs in a straight fight. This is still fair. The players decide, instead, that they will burn down the forest to get rid of the orcs. This is also fair. What wouldn't be fair in this scenario is for the GM to suddenly decide he doesn't like that solution, and that the trees in this forest are fireproof. Which isn't to say that a fireproof forest is unfair per se, but the players should probably have been able to discover that fact before venturing into it, which they can't if it's by fiat.
On the other hand, in a CAS game, the players encountering this orc horde is arguably unfair in most circumstances, assuming that it's reasonable that they would want to stop the horde. There's an expectation that the GM won't put obstacles in their way that they don't have the means to overcome, and even if the players think of burning down the forest, it might not fit with the group's ideology (a good-aligned ranger/druid party for example). It's typically not in the spirit of this type of game for the GM to force the players into an unwinnable scenario.
Of course, I've yet to see a game that was pure CAW or pure CAS. The games I've been in have always fallen between those two extremes.
I think that CAW falls closest to Kirk's version of the Kobayashi Maru, as the expectation at the table is that you may be presented with an unwinnable scenario and therefore must alter the conditions of the test in order to win. Even there though, there are scenarios that can be unfair. We can imagine a campaign that begins with the players locked in a room with a 100 tarrasques. It's CAW taken to the extreme, but it's not really in the spirit of CAW. Odds are that no matter how many times you play through that scenario, it will end the same way regardless of what the players choose to do (assuming they get to make a choice at all). Even for CAW, a real Kobayashi Maru (where players can't change the conditions of the test, and therefore automatically doomed to fail) is probably not in the spirit of the game.
Both CAS and CAW are both valid and fun preferences, and as I've said, I can't think of a game I've played that was purely one or the other. However, games that are closer to the CAS end of the spectrum have a stricter concept of fairness than game that are more CAW. What might be fair in a CAW game isn't necessarily fair in a CAS game.