Well, I was pretty sure, yes.
I think there was a lot of GM-facing stuff (systems and advice) published in the 90s and probably early-aughts that prioritized things the way you're describing. I think most people now look at that as something of a nadir; players found it unsatisfying, rules and advice were written differently.
A lot of the people picking apart 5E on these fora seem to me like generals fighting some previous war. Or, possibly, they're proving correct Faulkner's comments about the past.
I do not think that sort of GMing is more-supported in the text of the rules than any other, and I think it's actually deprecated in some of the subtext. The adventures are a different thing, of course, and often published adventures--especially long ones--are really poor examples of what can/should emerge from play; even if a table is playing a long, published adventure, though, I don't think the rules are written in ways to encourage the kind of action-negation you're talking about.
(That said, there's an "Adventure Flowchart" in the new Guide to Ravenloft book that is ... entirely linear, with no branches at all. That ... is not a flowchart, and it's a really crappy example of adventure/scenario design.)
I think the majority playstyle in 5E (if there is one) is the long, published adventures. Given that "PLAY GUD" in that context means "GET TO THE END OF THE ADVENTURE AND BEAT THE BBEG" I'm not sure there's quite the conflict even there that you think there is--I don't really see the appeal, though, and I avoid such games if at all possible, so someone else would have to elaborate on that.
Rambling on form this point -
If the linear adventure has a single overarching clock, it
would be possible, through skillful play, for the pc's to get so far ahead of the timer they can take an extra long rest, right before the BBEG, and thus go in to the fight with significantly more resources than originally expected by the designers.
In other words, they could have "earned" an extra long rest, from a certain point of view.
In this case - if the dm cares about challenge at all - the long rest should be granted. They earned it. It might make the last fight less exciting in the oh-no-this-guy's-tough sense, but that's because compared to the party and players, he's not. The adventure, as a whole, was not hard for them, and forcing the last battle to be extra tough by fudging the rules won't change that.
On top of that, such fudging would, if noticed by the players (and the odds of such are pretty good if the players know the rules of the game and knew the risks of long resting), will invalidate the entire challenge, such as it was, up to that point. You make the victory, or defeat, hollow, since you have negated the skill of the players as a factor in how things turn out.
"Yeah, we got so far ahead we were able to long rest in Strahd's own bedroom before we stomped on him!" is a better story than "We were doing great until the dm decided to take away a rest just to make the last fight 'fair' for Strahd."
Ergo, the best decision, IMO, is to let the players take their victory lap. It's fair to them, a good story, and the most fun option.
On the other hand, an adventure path that allows for such an outcome is poorly designed at some level. Either the last run of adventures simply shouldn't allow for long rests (pretty easy to do by setting a Clock when the pc's enter the final dungeon) or should already be tune-able to account for differing levels of player skill (essential to any game of DnD.
My vote has not changed, though I think I'm getting better at articulating why.