Maybe I should have qualified a little further.
Starfleet has military and science missions. The USS Enterprise was not a warship. They have the Dreadnought class for that. The USS Enterprise has been a flagship vessel of exploration, not a battleship. Now, that does not preclude the Enterprise from engaging in battle. It has to be prepared for that. And it has been... we've seen it go into battle before. But it's not the primary mission.
Anytime a vessel has a commander, he sets the tone and structure for how his command will be. The crew acclimates to it. It doesn't happen in just a few days. It takes time. Jellico came on board and started making drastic changes, expecting the crew to fall in line in just one day. And for what? Is it common practice for a Starfleet vessel to operate on a 4 shift rotation? What's wrong with 3 shifts? Certainly the Enterprise crew demonstrated their ability to handle it. Yes, the Enterprise doesn't end up in battle, because Jellico manages to negotiate well enough to avoid it. But had they gone into battle, I'll bet anything that the main structure is a 3 shift rotation, but other crew members will do double-shifts in a pinch.
Jellico made a demand upon the ship that didn't seem to be truly warranted. He didn't make any kind of clear assessment that the crew couldn't handle the job with a 3 shift rotation. It's Jellico who is used to operating things that way and wanted to make the change purely because of that. Jellico can't rip everything apart in short notice and expect it all to run smoothly.
It's not nonsense. TDY or permanent, they'd have the same ceremony. Jellico was taking over for an undisclosed period of time, not "in a pinch." I know that Starfleet didn't specify it as TDY, but it ended up being so. Wasn't that their intention all along? Or were they expecting that the chances of Picard returning weren't very good? If Picard is one of the best Starfleet captains, why "throw him away" on such a mission, when he's a very valuable asset? I think they had great trust in Picard and expected that he would return.
Anyway, I won't push this part. It's not as important as the other point about readiness and Jellico's unwillingness to be flexible with the situation.
Entenman's makes a pretty good lemon poppy seed cake.