No. I find it disingenuous. If I have built an encounter, and the group runs through it, so be it. If I built an encounter and the group nearly dies, so be it. I always err on the side of caution when building an encounter and try to add more things that are interesting than deadly. But the last thing I worry about are the swing of the dice. That, at least to me, is part of the fun of the game. If we wanted to tell a story with predicted outcomes, we would choose a different game.
I can see some people's wheels turning about how a DM screen doesn't mean the DM fudges rolls. No offense, but I call bull. It may be my experiences, but every time I've played with a DM that uses the screen, magically, the big-boss battles are hair-tight and only at the last second does the group win. And in those moments when the big-bad managed to get another round or two because of bad player rolls, the big-bad either does something stupid (even though they are brilliant) or they magically miss a bunch. Meanwhile, all the DMs I've played with that don't use a screen, the battles go exactly as the dice go. It doesn't mean you die, but if your third level and miss three times in a row, and the rest of your group is rolling poorly, you're in trouble. With the no screen DM, I've seen TPKs, reboots (as in that went horribly bad, let's make it all a vision you had that night), divine interventions, etc. With screened DMs, that doesn't happen.