Jester David
Hero
A second level spell slot isn't much of a limited resource at high levels.I fail to see how spending a limited resource to create a safe place to short rest is pushing anybody. Why should the DM give a dusty flumph about this at all? It sounds to me like they fairly prepared and executed well and deserve the benefits.
The job of the DM is to tell the story, challenge the PCs, and encourage the fun of the players.
If the PCs are using said spell to rest in an unexpected time, that reduces or even negate some of the challenge. And it might lead to the remainder of the story could be anticlimatic, while reducing the tension. This diminishes the fun. Thus, it's in the best interests of the DM to limit that.
Or do something to restore the challenge and increase the tension.
Now, if the PCs need the rest to even succeed and not die—such as recovering from bad rolls or some tactical mistakes—then it might be in the best interests of the DM to let the tactic succeed.
It's up to the DM to look at how rope trick is being used in each situation and decide what will be the most fun at the table.