I did find that kind of odd. When Bungie was making Halo 3 they had to basically rebuild all their graphical assets from the ground up since they were dealing with a new generation of hardware and could increase poly counts, use higher-res textures, add more details, etc. However, most returning assets looked extremely similar to their Halo 2 counterparts. Except for the number of bolts in the hands and feet and of course the layer of then-next-gen polish, the Chief's armor looks nearly identical to how it did in Halo 2. The Covie weapons are as faithful as can be to their Halo 2 versions. The UNSC weapons are all very close to their Halo 2 versions. The Grunts' skin texture was changed to make them more closely resemble the quasi-arthropods they were described as years earlier, but otherwise they are damn close to their Halo 2 versions. Not everything was faithful to the original designs (the Elites and especially Brutes), but at the very least Halo 3 demonstrates that even with far more advanced tech at your disposal it's very possible to have the newer, higher-poly, higher-res, higher-detail models stay faithful to the older simpler models.

: But yeah. Halo 1 Magnum is back!

I know, right? So glad it's coming back as a power weapon in Warzone.