The update is the same size no matter which console you have. You download the xbox one x enhancements, but just cannot use them. Also, the additional 73 Gigs to download completely replaces the original 65 Gigs that it is now.
They basically re-wrote the whole game, so the update replaces what you have.
I'm not sure if you own the digital version or the disc version. But now the disc basically just operates as your 'license' to play.
While 73 Gigs is still pretty big, I know, you won't have to keep downloading huge patches in the future. The new intelligent delivery feature was the reason it had to be so parceled out and huge.