I purchased one text tone after the iOS 17 upgrade, mainly to see where the sound would wind up in the file system, what Ringtone.plist file would be affected, and what the data record in the plist would look like That said, this newly purchased text tone works as expected.
Once again, the problem with older text tones is missing entries in their data record in a Ringtomes.plist file. This is why “regenerating“ a text tone using the GarageBand technique works: it creates a new data record in the plist for the “new” tone which has all the correct entries required to make the tone accessible as a text tone.
IMO, the biggest issue with this bug is that customers who have actually paid Apple for text tones in the past are now being denied the ability to use them for their intended purpose.
As for the system default notification tone, AFAIK iOS has never allowed the end user to set an alternate sound for it, unlike Android. I never understood this design decision, because it flies in the face of personalization, resulting in every iPhone on the planet sounding identical when a notification occurs. I can’t tell you the number of times I’ve been in meetings, the default iPhone notification tone chimes, and everyone looks at their phone to see whether it was a notification for them versus the person sitting next to them. LOL!