Here's a shocking revelation: In non-contemporary times, generals and high-ranking officers did actually fight with their men. Napoleon, Caesar, Alexander the Great, the list is extremely long. From what I gather Ulfric and his men were ambushed and caught by Imperials, that shows that Ulfric atleast fights, which is more than I can say for Tullius. We also know Ulfric fought in the Great War. We know he's a brilliant general, but he might not necessarily have a lot of combat experience. He clearly wasn't leading any armies during the Great War.
Ulfric never fought during the Legion ambush because he did not fight in the first place. He and his men laid down their arms and were captured by the Imperials. Hadvar himself tells you this, and is just as surprised at the outcome as anyone especially since Ulfric was known for his whole 'never surrender' attitude.
And Tullius himself led the charge on Windhelm at the end of the civil war. Where was Ulfric at this time? In the keep with Galmar. Even when Tullius, Rikke, and the newly made Legate barge in, Galmar attacks first while Ulfric watches on the Throne.
It's not really negotiating when you're offering a treaty that has the same [unnegotiated] terms as an ultimatum that was given a few years before.
Let's take a quick look at the terms of the Concordat that we do know, and their consequences:
-The Empire cedes Hammerfell to the Dominion. (The Thalmor later made a treaty with Hammerfell and pulled out.)
-The Empire bans the worship of Talos. (It took the Thalmor twenty years before they realized the Empire was not enforcing the ban.)
-The Dominion will pull out of the Empire and its provinces. (This only allowed the Empire to repair its infrastructure and rebuild its armies.)
So Hammerfell is no longer part of the Empire, but it was in no shape to fight at the time. Even better, it is not part of the Dominion and they know who to fight when war breaks out again.
The Talos ban was engineered with spreading dissent in mind, but so far it has only brought about the civil war, which the Empire may put down easily or became a greater threat to the Thalmor depending on who you follow. One could argue that it allows the Thalmor to spy on the Empire, but that would happen even with no treaty. If they are spying, then atleast they are in plain sight.
And the peace guaranteed by the concordant will not last forever, and everyone knows this. Thirty years is enought time for humans to lick their wounds, even with the state Cyrodill was left in. But the elves, even with their cities intact, cannot hope to muster enough forces unless they call upon the aid of their provinces, which will yield trivial amounts of troops at best.
So you may say that the terms were still the same, but that never really mattered. What mattered was that the Empire struck the Dominion a mortal wound at Red Ring, one that will affect them into the next war.