why, other than a single ship( and cause it not the same ship IRL) the federation never did. A refit does not rebuild a ship, its normally just upgrades computers and maybe weapons. Most of the ships we saw before hand had RL reasons for the look, they were reused models or kitbashes based off store bought models. The TE can build connies now, it looks to me as if the Defiant's data base was how they kept pace with the Federation and always have the same ships. They would not Upgrade the original and not install those same upgrades on the copies. After all, its a heavy cruiser, meant to wade into battle. The ship may not even be in use any more, but the one they saw on the screen looked just like the one they knew as that was the only confusion "But its not been reported lost?"