Furthermore, an arms race is already in progress due to the current Cold War situation.
Which is exactly why the Federation's goal is to cool that process down, rather than exacerbate things. The reason the US-Soviet Cold War got so out of hand is because both
sides mistakenly thought they were defending against the other
side's aggressive intentions, so it became a vicious cycle. It was basically about mutual fear and paranoia. The Federation needs to convince the Typhon Pact that they don't have to be afraid of Federation attack, that the UFP has no intention of invading, conquering, or oppressing them and will leave them alone as long as they leave the UFP alone. Unilaterally embracing a superweapon from the future is exactly the wrong way to do that.
All I have to base my judgement are the FX from Endgame and STO.
Well, the thing about STO is that it's basically a combat game, so it's biased toward the escalation of military situations. Naturally that's not the mentality one would expect from the Federation in a more plausible fictional context.