Ver.5.6.22 - why is it "adding and updating files" when modifying metadata?

[Panther]

I was trying to finish some metadata updates I was in the middle of with 5.6.22 before updating to 5.7.2, and I ran into a weird behavior tonight.

Basically, all I was doing was changing some of the date-related metadata in my production database (cleaning up after some of the experiments I was running over the past few weeks and converting to use a more normal/traditional approach to date entries so I could use the timeline function more reliably).

Everything seemed to be going OK, and I was generally writing back the metadata in groups of 50-100 files at a time (I have auto write back turned off and use the command menu to have it write back the metadata for all pending files).  But two or three times after I told it to write back the metadata  I saw in the status bar at the bottom right corner that it was going through a multi-minute process of adding and updating files (the same message I would see if I had actually added new files to the database, although I had not done so). 

I don't remember seeing that particular type of message when I was just telling it to write-back metadata - is it normal to display that message just because it is writing back a number of files, or is something else weird going on to cause it to think it's actually adding files?  It kinda freaked me out that it seemed to think it was seeing new files to add when I had not added any files to the database folders.

[Mario]

Wiring back metadata always triggers an immediate re-import of the files. This way IMatch gets the final metadata produced by ExifTool into the database.
Sometimes additional rescans are triggered by Windows (e.g. Windows updating the thumbnail database files in the folder after noticing that files were updated). Nothing unusual.
If you are really bothered you can check in the IMatch log file which files were added / updated. Search for AddOrUpdateFile.

[Panther]

Thanks!

Good to know it's just a normal part of the process.