The label is critical here. This does not mean the disc is a native 4K UHD BluRay (though that exists separately). Instead, Sony Pictures (who distributed the film) went back to the original 35mm camera negatives. They scanned the film at 4K resolution (4096 x 3112 pixels) to create a new digital intermediate. They then downscaled that pristine 4K scan to 1080p.
Just remember: Support the official release if you can. The Sony "Mastered in 4K" BluRay disc is still in print. But for your digital library, the x264 dual rip ensures that the King of the Monsters... sorry, Zilla ... looks better than he ever has on screen. godzilla 1998 mastered in 4k 1080p bluray x264 dual