Well, it still wouldn't make sense that the treaty of the original war would have any sort of a clause about cloaking devices. Back then, invisibility technology supposedly didn't exist, or at least the Feds didn't believe in it - so it would have been idiotic of the Romulans to insist on a cloaking ban back then if they were the only ones involved who even knew that invisibility was viable!
Of course, ENT later established (and IMHO rightly so) that invisibility tech is relatively common and ancient in the galaxy, even if the heroes and main villains don't have it yet. And it went on establishing that Romulans had invisibility already during the war. So in hindsight, the cloaking treaty could be the original treaty could be Algeron... But the writers of "Pegasus" wouldn't have been thinking in those terms yet.
As for how "Pegasus" describes the treaty, the episode never mentions Tomed or the year 2311 specifically. It only says that the treaty has kept peace for 60 years, which would very roughly match up with 2311 - thus, people have preferred to associate the treaty with Tomed. And Tomed was only ever mentioned in "The Neutral Zone"...
Timo Saloniemi
Actually, in ENT it is established in dialogue that the Treaty of Algeron was signed in 2311. TATV in case you didn't figure which episode I was referring to.