Why Does My Takeout Have Folders I Do Not Recognise?
Untitled albums, Archive, Bin and year folders. Here is what each one actually holds.
Your export contains Google's own filing system, which you never saw in the app.
Photos from 2015 and similar are your main library, split by year. Archive holds photos you archived: hidden from the grid but never deleted, and almost certainly worth keeping. Bin or Trash holds recent deletions, so check it before merging or you will resurrect things on purpose deleted. Untitled folders are usually albums you never named. And every album folder has a small metadata.json describing the album rather than a photo.
None of it is corruption. It is just Google's structure rather than yours.
Point the app at the folders you actually want and it builds a single clean library from them, with the real dates and locations written into every photo. You decide what comes along and what stays behind. The first 500 photos are free.