I have figured out that this is because macOS Monterey (for some reason) does not allow the first letter of a user account name to be capitalized as was standard on past macOS versions. The existing files all have my user capitalized in the file path, as my account name displayed on previous macOS versions, where the new duplicates have the user in all lower-case in the file path.
For some reason, the playlist side of Rekordbox file handling is not case sensitive, where it would appear the file path IS case sensitive on the import side. This would be why my files will load, but the import doesn't recognize the files as being the same.
I was able to fix this by creating a new folder in user/Music, dropping my entire collection into that folder, and then from the Missing Files dialog auto relocating all the files. Then once that was done, moving the collection back, and auto relocating again. This left about 15-20 files remaining in my collection that for some reason were left with the old, capitalized file path, but that is easy enough to deal with and replace into their appropriate playlists.
Figured I would post this for anyone else since Rekordbox support is virtually non-existent even though we paid thousands of dollars for the players that essentialy require its use. This is exactly why Pioneer DJ is losing market share to Denon, hope someone is paying attention over there....