The c:\system volume information folder is normally a hidden, protected, folder (unless you changed that), only used by system restore.
Even though there may have proven to be false positives, the c:\system volume information folder is also protected by system restore and I would imagine this is why avast can't put them back in there.
Even if you were able to un-hide the folder you couldn't just dump them back in there if system restore didn't block you, as the restore point has to be integrated into the system restore function or it wouldn't be visible/usable to system restore. So personally I believe there would be little purpose in trying to do this.
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- Infected/Suspect Restore Points - There really is little benefit in chasing a detection in the system volume information folder. It is only there because it had previously been deleted or moved from the system folders and this is a back-up created by system restore.
- Worst case scenario it isn't infected and you delete it, you can't use that restore point in the future (much the same if you actually were able to extract the file there), not much of a loss and the older the restore point is the less of an issue it is.
- So if there is any suspicion about a restore point then it is best removed from the system volume information folder or it could bite you in the rear at some point in the future when you use system restore if it included that restore point.