Forward Unto Dawn - Halo 4 compared to Halo 3

I’ve just played through Halo 3 again and then started up Halo 4 again as well. I couldn’t help but notice that the Forward Unto Dawn in Halo 4 looks completely different to how it looked in Halo 3.

Bungie kept things like this consistent. In Halo Reach, the Savannah was also a Frigate and looked like FUD and In Amber Clad (also a Frigate). 343 come along and suddenly a frigate no longer looks like a frigate. Small thing I know, as FUD is barely even in Halo 4.

Also, how did the new weapons, like the new BR (which is a new model commissioned after the Covenant War) get on the FUD? They are usable before Infinity reaches Requium.

Basically, just small continuity issues I have. 343 can do what they want with new vehicles/weapons/ships after the Covenant War as it can be explained as decommissioning the old vehicles/weapons/ships and them being replaced with newer models after 2553 (like the new Pelicans). But to change the established look of Frigates from during the Covenant War for the sake of change just seems odd.