none of the new features appear in game except for the new inventory style, the game says that there there in the files or that the textures are loaded in but it doesn't show up in the inventory or using commands.
(screenshots below but all of the new items added in the snapshot are missing)
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When creating a new world, you need to enable the 1.20 content data pack as well to be able to access the new stuff. See MC-256552 for more information.
Read the blog post again...
You must enable the experimental feature data pack(s) to get these features...