The Federation has a vested interest in peace, as has been made clear through the course of multiple series. By that standard it's in their own best interests to interpret the treaty liberally rather than aggravate the Romulans with some bullshit line (even if it were honest), that cloaking is just a "secondary effect".
What you're calling bullshit is what most of us name consensus reality. I notice that, not even once, have you dealt with the examples of technology I provided that are clearly not, first and foremost, cloaking tech, that may have a cloaking effect as an unintended secondary effect (yes, that is a reasonable phrase; an instance such as this one is exactly why we have such words in the English language as "primary" and "secondary")--except to say, somewhat hilariously, that yes, they would be considered cloaks. Warp 10+ drive that happens to have a cloaking effect is a cloaking device. Hoo boy.
This is because you can't deal with these examples--your inflexible position that the exact letter of a law (and a treaty is a kind of law) is open to no interpretation at all under peculiar circumstances is at odds with both the reality of court systems the world over and with international treaty arbitration.
It is clearly not
in the Federation's best interests, however peace loving they may be (and it's worth pointing out that the Romulans are a party to the treaty as well, so, by your lights, they must be "peace loving" as well) to give the Romulans a ludicrous veto over any tech development that just might happen
to produce something invisible to them. It doesn't even make sense in the context of a treaty designed, as you say, to preserve peace. That wouldn't be "peace"--it'd be surrender.
I see no evidence that either the Federation or Starfleet is ruled at its highest echelons by Pollyannas and fools. Only one or the either would bind themselves to an interpretation of a treaty so laughably broad it takes no actual note of the treaty's original purpose, and has it serve instead as some sort of combination one-sided disarmament and catchall technological repression agreement.