The problem with short rest classes is that it’s the long rest classes who set the pace. Yes, theoretically the warlock can take enough short rests over the course of a day to cast more spells than the wizard can. But not if the wizard uses up all their spells before the warlock has had a chance to take a single short rest and then demands the party call it quits for the day.
It’s the same problem as daily vs. at-will. At-will classes need a certain number of encounters to happen in a day to keep up with the daily characters’ damage output. Which means if the daily characters decide the day is done before that number of encounters have happened, the at-will character falls behind. Short rest characters have the same problem, only they’re also capped in how much damage they can output in a single encounter. A dungeon crawl just happens to be a context where the daily characters will have a harder time convincing their at-will and short rest companions that going to bed after one fight is a safer idea than continuing on.