So what's the other features and bug fixes? Who cares about a wallpaper, I want to know the features and fixes. I swear apple is so centered on wallpapers and stickers, why not center on the phone as a phone. I'm surprised they didn't release a snoopy wallpaper to match the watch.
Apple will often add security detail changes well after the fact in order to help prevent people who have not yet updated from being vulnerable to zero-day vulnerabilities. But you can see the ones that they publish here:
https://support.apple.com/en-us/HT214101
If they don't mention features, they obviously haven't added any (beyond the updates to News+ and tracking detection that they do list).
I do think that Apple should be more transparent about bug fixes, but it's possible that they number in the several dozen minor fixes so they probably don't want to either highlight them, or they know that the vast majority of users probably don't care about that level of detail.
I do guess that 17.5 was also required for iPadOS in order to support the new iPad models and devices (e.g., the new pencil and Magic Keyboard) coming tomorrow, and Apple likes to keep the two OSes at the same level for the first and second numbers at least.