I can see two reasons for not using "I break free" as the verbal:
1) It doesn't actually communicate to new players what's going on; if they don't already know that Escape Act exists and that it uses that call, they may think it's simply some ability everyone has, or perhaps a skill they overlooked, or they may call a hold anyway just to find out what the heck you just did (particularly in the case of a new NPC).
2) It doesn't use what I'm going to call the "standard magic item verbal"; many magic items that have a verbal component to announce their activation require you to say "Activate" before you use them, and those that don't usually have you either say the name of the Ritual itself (Trap Avoidance comes to mind, even though that's during a hold) or a specific word or phrase that explains exactly what just happened in clear and concise manner ("Absorbed" for Spell Store), all of which make it quite clear that a magic item is being used and exactly what the effect of that magic is. "I break free" uses neither of the first two conventions, but it also falls short of the third convention by not clearly identifying that a magic item is being used; "Activate, I break free" is only marginally better, but at that point you might as well just make the verbal be "Escape Act".
On a tangential note, even monsters don't use "I break free" to escape Binding effects (and most monsters can rip from at least some of them), so if we were going to use it, the verbal would likely end up being "I rip from [Effect]" on a 1-count rather than create a whole new call for this magic item, but that also has the potential for confusion noted in point 1 unless you include "Activate", at which point once again you might as well just make the call "Escape Act" and save the time.
Not to toot my own horn too loudly, but "Activate Escape Act, Release" is short, easy to say and remember, follows the usual verbals for activating magic items, and clearly explains what effect took place. It's not perfect, but I would consider it on par with the "Elemental Release" call suggested by Draven (although I feel I should note here that if the intent of the Ritual is that it affects you the same way a Potion does, the Qualifier should technically be Spell, not Elemental, although I also understand why Elemental would likely be a preferable Qualifier over Spell for this, and I also feel that it should require "Activate" as part of the verbal).