I think a good example is Nightfalls in Destiny. In D1 Nightfalls were fairly tough unless you way outgeared them or cheesed them, but they could be done if you were smart about the fights. There was no timer, it was just tough enemies. Then when D2 came out Nightfalls initially were timed, which made them far more difficult to my group (none of us like rushing) even though the enemies were way weaker and fights way easier. The timer adds artificial difficulty by forcing you to play sloppy. So it was both more boring, due to the far less challenging enemies, and more stressful, due to the timer. Needless to say, we all preferred the D1 Nightfall design. I think D2 ended up going back to that, but by then we were already soured on the game.
So yeah, I think the same could apply here. I find mechanically difficult fights much more engaging than timed fights, but whatever. Who knows, maybe most people genuinely like feeling rushed.