Disk Utility message "Updating boot support partitions for the volume as required"

Finder crashed on a external drive which caused an abrupt eject. I rand Disk Utility over the drive and the operation finished with the message:

Updating boot support partitions for the volume as required

Its a FAT32 partition, it already existed, and it was not bootable so its not clear to me what required updating.

What does the message "Updating boot support partitions for the volume as required" mean? Or how can I determine the changes were made?

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